Sorting algorithms/Pancake sort
You are encouraged to solve this task according to the task description, using any language you may know.
Sorting Algorithm
This is a sorting algorithm. It may be applied to a set of data in order to sort it.
For comparing various sorts, see compare sorts.
For other sorting algorithms, see sorting algorithms, or:
Heap sort | Merge sort | Patience sort | Quick sort
O(n log2n) sorts
Shell Sort
O(n2) sorts
Bubble sort |
Cocktail sort |
Cocktail sort with shifting bounds |
Comb sort |
Cycle sort |
Gnome sort |
Insertion sort |
Selection sort |
Strand sort
other sorts
Bead sort |
Bogo sort |
Common sorted list |
Composite structures sort |
Custom comparator sort |
Counting sort |
Disjoint sublist sort |
External sort |
Jort sort |
Lexicographical sort |
Natural sorting |
Order by pair comparisons |
Order disjoint list items |
Order two numerical lists |
Object identifier (OID) sort |
Pancake sort |
Quickselect |
Permutation sort |
Radix sort |
Ranking methods |
Remove duplicate elements |
Sleep sort |
Stooge sort |
[Sort letters of a string] |
Three variable sort |
Topological sort |
Tree sort
- Task
Sort an array of integers (of any convenient size) into ascending order using Pancake sorting.
In short, instead of individual elements being sorted, the only operation allowed is to "flip" one end of the list, like so:
Before: 6 7 8 9 2 5 3 4 1
After: 9 8 7 6 2 5 3 4 1
Only one end of the list can be flipped; this should be the low end, but the high end is okay if it's easier to code or works better, but it must be the same end for the entire solution. (The end flipped can't be arbitrarily changed.)
Show both the initial, unsorted list and the final sorted list.
(Intermediate steps during sorting are optional.)
Optimizations are optional (but recommended).
- Related tasks
- Also see
- Wikipedia article: pancake sorting.
11l
<lang 11l>V tutor = 1B
F pancakesort(&data)
I data.len <= 1
R
I :tutor
print()
L(size) (data.len .< 1).step(-1)
V maxindex = max(0 .< size, key' x -> @data[x])
I maxindex + 1 != size
I maxindex != 0
I :tutor
print(‘With: #. doflip #.’.format(data.map(x -> String(x)).join(‘ ’), maxindex + 1))
data.reverse_range(0 .< maxindex + 1)
I :tutor
print(‘With: #. doflip #.’.format(data.map(x -> String(x)).join(‘ ’), size))
data.reverse_range(0 .< size)
I :tutor
print()
V data = ‘6 7 2 1 8 9 5 3 4’.split(‘ ’) print(‘Original List: ’data.join(‘ ’)) pancakesort(&data) print(‘Pancake Sorted List: ’data.join(‘ ’))</lang>
- Output:
Original List: 6 7 2 1 8 9 5 3 4 With: 6 7 2 1 8 9 5 3 4 doflip 6 With: 9 8 1 2 7 6 5 3 4 doflip 9 With: 4 3 5 6 7 2 1 8 9 doflip 5 With: 7 6 5 3 4 2 1 8 9 doflip 7 With: 1 2 4 3 5 6 7 8 9 doflip 3 With: 4 2 1 3 5 6 7 8 9 doflip 4 With: 3 1 2 4 5 6 7 8 9 doflip 3 With: 2 1 3 4 5 6 7 8 9 doflip 2 Pancake Sorted List: 1 2 3 4 5 6 7 8 9
AArch64 Assembly
<lang AArch64 Assembly> /* ARM assembly AARCH64 Raspberry PI 3B */ /* program mergeSort64.s */
/*******************************************/ /* Constantes file */ /*******************************************/ /* for this file see task include a file in language AArch64 assembly */ .include "../includeConstantesARM64.inc"
/*********************************/ /* Initialized data */ /*********************************/ .data szMessSortOk: .asciz "Table sorted.\n" szMessSortNok: .asciz "Table not sorted !!!!!.\n" sMessResult: .asciz "Value : @ \n" sMessCounter: .asciz "sorted in @ flips \n" szCarriageReturn: .asciz "\n"
.align 4 TableNumber: .quad 1,3,11,6,2,-5,9,10,8,4,7
- TableNumber: .quad 10,9,8,7,6,-5,4,3,2,1
.equ NBELEMENTS, (. - TableNumber) / 8
/*********************************/ /* UnInitialized data */ /*********************************/ .bss sZoneConv: .skip 24 /*********************************/ /* code section */ /*********************************/ .text .global main main: // entry of program
ldr x0,qAdrTableNumber // address number table mov x1,0 // first element mov x2,NBELEMENTS // number of élements bl pancakeSort ldr x0,qAdrTableNumber // address number table bl displayTable mov x0,x10 // display counter ldr x1,qAdrsZoneConv bl conversion10S // décimal conversion ldr x0,qAdrsMessCounter ldr x1,qAdrsZoneConv bl strInsertAtCharInc // insert result at @ character bl affichageMess // display message ldr x0,qAdrTableNumber // address number table mov x1,NBELEMENTS // number of élements bl isSorted // control sort cmp x0,1 // sorted ? beq 1f ldr x0,qAdrszMessSortNok // no !! error sort bl affichageMess b 100f
1: // yes
ldr x0,qAdrszMessSortOk bl affichageMess
100: // standard end of the program
mov x0,0 // return code mov x8,EXIT // request to exit program svc 0 // perform the system call
qAdrsZoneConv: .quad sZoneConv qAdrszCarriageReturn: .quad szCarriageReturn qAdrsMessResult: .quad sMessResult qAdrTableNumber: .quad TableNumber qAdrszMessSortOk: .quad szMessSortOk qAdrszMessSortNok: .quad szMessSortNok qAdrsMessCounter: .quad sMessCounter /******************************************************************/ /* control sorted table */ /******************************************************************/ /* x0 contains the address of table */ /* x1 contains the number of elements > 0 */ /* x0 return 0 if not sorted 1 if sorted */ isSorted:
stp x2,lr,[sp,-16]! // save registers stp x3,x4,[sp,-16]! // save registers mov x2,0 ldr x4,[x0,x2,lsl 3]
1:
add x2,x2,1 cmp x2,x1 bge 99f ldr x3,[x0,x2, lsl 3] cmp x3,x4 blt 98f mov x4,x3 b 1b
98:
mov x0,0 // not sorted b 100f
99:
mov x0,1 // sorted
100:
ldp x3,x4,[sp],16 // restaur 2 registers ldp x2,lr,[sp],16 // restaur 2 registers ret // return to address lr x30
/******************************************************************/ /* flip */ /******************************************************************/ /* x0 contains the address of table */ /* x1 contains first start index /* x2 contains the number of elements */ /* x3 contains the position of flip */ flip:
//push {r1-r6,lr} // save registers
stp x1,lr,[sp,-16]! // save registers
stp x2,x3,[sp,-16]! // save registers
stp x4,x5,[sp,-16]! // save registers
str x6, [sp,-16]! // save registers
add x10,x10,#1 // flips counter
cmp x3,x2
sub x4,x2,1
csel x3,x4,x3,ge // last index if position >= size
1:
cmp x1,x3 bge 100f ldr x5,[x0,x1,lsl 3] // load value first index ldr x6,[x0,x3,lsl 3] // load value position index str x6,[x0,x1,lsl 3] // inversion str x5,[x0,x3,lsl 3] // sub x3,x3,1 add x1,x1,1 b 1b
100:
ldr x6, [sp],16 // restaur 1 register ldp x4,x5,[sp],16 // restaur 2 registers ldp x2,x3,[sp],16 // restaur 2 registers ldp x1,lr,[sp],16 // restaur 2 registers ret // return to address lr x30
/******************************************************************/ /* pancake sort */ /******************************************************************/ /* x0 contains the address of table */ /* x1 contains first start index /* x2 contains the number of elements */ pancakeSort:
stp x1,lr,[sp,-16]! // save registers stp x2,x3,[sp,-16]! // save registers stp x4,x5,[sp,-16]! // save registers stp x6,x7,[sp,-16]! // save registers stp x8,x9,[sp,-16]! // save registers sub x7,x2,1 // last index
1:
mov x5,x1 // index mov x4,0 // max mov x3,0 // position mov x8,1 // top sorted ldr x9,[x0,x5,lsl 3] // load value A[i-1]
2:
ldr x6,[x0,x5,lsl 3] // load value cmp x6,x4 // compare max csel x4,x6,x4,ge // max = A[i} csel x3,x5,x3,ge // position = index cmp x6,x9 // cmp A[i] A[i-1] sorted ? csel x8,xzr,x8,lt // no mov x9,x6 // A[i-1] = A[i] add x5,x5,1 // increment index cmp x5,x7 // end ? ble 2b cmp x8,1 // sorted ? beq 100f // yes -> end cmp x3,x7 // position ok ? beq 4f // yes cmp x3,0 // first position ? beq 3f bl flip // flip if not greather in first position
3:
mov x3,x7 // and flip the whole stack bl flip
4:
//bl displayTable // to display an intermediate state subs x7,x7,1 // decrement number of pancake bge 1b // and loop
100:
ldp x8,x9,[sp],16 // restaur 2 registers ldp x6,x7,[sp],16 // restaur 2 registers ldp x4,x5,[sp],16 // restaur 2 registers ldp x2,x3,[sp],16 // restaur 2 registers ldp x1,lr,[sp],16 // restaur 2 registers ret // return to address lr x30
/******************************************************************/ /* Display table elements */ /******************************************************************/ /* x0 contains the address of table */ displayTable:
stp x1,lr,[sp,-16]! // save registers stp x2,x3,[sp,-16]! // save registers mov x2,x0 // table address mov x3,0
1: // loop display table
ldr x0,[x2,x3,lsl 3] ldr x1,qAdrsZoneConv bl conversion10S // décimal conversion ldr x0,qAdrsMessResult ldr x1,qAdrsZoneConv bl strInsertAtCharInc // insert result at @ character bl affichageMess // display message add x3,x3,1 cmp x3,NBELEMENTS - 1 ble 1b ldr x0,qAdrszCarriageReturn bl affichageMess mov x0,x2
100:
ldp x2,x3,[sp],16 // restaur 2 registers ldp x1,lr,[sp],16 // restaur 2 registers ret // return to address lr x30
/********************************************************/ /* File Include fonctions */ /********************************************************/ /* for this file see task include a file in language AArch64 assembly */ .include "../includeARM64.inc" </lang>
Value : -5 Value : +1 Value : +2 Value : +3 Value : +4 Value : +6 Value : +7 Value : +8 Value : +9 Value : +10 Value : +11 sorted in +17 flips Table sorted.
Ada
<lang Ada>with Ada.Text_IO; procedure Pancake_Sort is
generic
type Element_Type is private;
type Index_Type is range <>;
type Array_Type is array (Index_Type range <>) of Element_Type;
with function ">" (Left, Right : Element_Type) return Boolean is <>;
procedure Pancake_Sort (Data: in out Array_Type);
procedure Pancake_Sort (Data: in out Array_Type) is
procedure Flip (Up_To : in Index_Type) is
Temp : constant Array_Type := Data (Data'First .. Up_To);
begin
for I in Temp'Range loop
Data (I) := Temp (Temp'First + Up_To - I);
end loop;
end Flip;
Max_Index : Index_Type;
begin
for I in reverse Data'First + 1 .. Data'Last loop
Max_Index := Data'First;
for A in Data'First + 1 .. I loop
if Data(A) > Data (Max_Index) then
Max_Index := A;
end if;
end loop;
if Max_Index /= I then
if Max_Index > Data'First then
Flip (Max_Index);
end if;
Flip (I);
end if;
end loop;
end Pancake_Sort;
type Integer_Array is array (Positive range <>) of Integer; procedure Int_Pancake_Sort is new Pancake_Sort (Integer, Positive, Integer_Array); Test_Array : Integer_Array := (3, 14, 1, 5, 9, 2, 6, 3);
begin
Int_Pancake_Sort (Test_Array);
for I in Test_Array'Range loop
Ada.Text_IO.Put (Integer'Image (Test_Array (I)));
end loop;
Ada.Text_IO.New_Line;
end Pancake_Sort;</lang>
Output:
1 2 3 3 5 6 9 14
ALGOL 68
<lang algol68>PROC flip = ([]INT s, INT n) []INT:
BEGIN
[UPB s]INT ss := s;
INT temp;
FOR i TO n OVER 2 DO
temp := ss[i];
ss[i] := ss[n-i+1];
ss[n-i+1] := temp
OD;
ss
END;
PROC pancake sort = ([]INT s) []INT:
BEGIN
INT m;
[UPB s]INT ss := s;
FOR i FROM UPB s DOWNTO 2 DO
m := 1;
FOR j FROM 2 TO i DO
IF ss[j] > ss[m] THEN
m := j
FI
OD;
IF m < i THEN
IF m > 1 THEN
ss := flip (ss,m)
FI;
ss := flip (ss,i)
FI
OD;
ss
END;
[10]INT s; FOR i TO UPB s DO
s[i] := ENTIER (next random * 100-50)
OD; printf (($"Pancake sort demonstration"l$)); printf (($"unsorted: "10(g(4) )l$, s)); printf (($"sorted: "10(g(4) )l$, pancake sort(s))) </lang>
- Output:
Pancake sort demonstration unsorted: -26 +41 -4 +21 +8 -2 +31 -47 -41 -7 sorted: -47 -41 -26 -7 -4 -2 +8 +21 +31 +41
AppleScript
Algorithm gleaned from Phix and that from Euphoria
<lang applescript>on pancake_sort(aList)
script o
property lst : aList
property len : (count my lst)
on flip(n)
if (n < len) then
set my lst to (reverse of items 1 thru n of my lst) & (items (n + 1) thru len of my lst)
else
set my lst to reverse of my lst
end if
end flip
end script
repeat with i from (count o's lst) to 2 by -1
set maxIdx to 1
set maxVal to beginning of o's lst
repeat with j from 2 to i
tell item j of o's lst
if (it > maxVal) then
set maxIdx to j
set maxVal to it
end if
end tell
end repeat
(* Performancewise, there's little to choose between doing the two 'if' tests below every time and
occasionally flipping unnecessarily. The flips themselves are of of course a daft way to achieve:
set item maxIdx of o's lst to item i of o's lst
set item i of o's lst to maxVal
*)
-- if (maxIdx < i) then
-- if (maxIdx > 1) then ¬
o's flip(maxIdx)
o's flip(i)
-- end if
end repeat
return o's lst
end pancake_sort
-- Task code: local pre, post, astid, output set pre to {} repeat 20 times
set end of pre to (random number 100)
end repeat set post to pancake_sort(pre)
set astid to AppleScript's text item delimiters set AppleScript's text item delimiters to ", " set output to "Before: {" & pre & ("}" & linefeed & "After: {" & post & "}") set AppleScript's text item delimiters to astid return output</lang>
- Output:
<lang applescript>"Before: {23, 72, 40, 43, 91, 38, 23, 58, 26, 59, 12, 18, 27, 39, 69, 74, 11, 41, 3, 40} After: {3, 11, 12, 18, 23, 23, 26, 27, 38, 39, 40, 40, 41, 43, 58, 59, 69, 72, 74, 91}"</lang>
ARM Assembly
<lang ARM Assembly> /* ARM assembly Raspberry PI */ /* program pancakeSort.s */
/* REMARK 1 : this program use routines in a include file see task Include a file language arm assembly for the routine affichageMess conversion10 see at end of this program the instruction include */
/* for constantes see task include a file in arm assembly */ /************************************/ /* Constantes */ /************************************/ .include "../constantes.inc"
/*********************************/ /* Initialized data */ /*********************************/ .data szMessSortOk: .asciz "Table sorted.\n" szMessSortNok: .asciz "Table not sorted !!!!!.\n" sMessResult: .asciz "Value : @ \n" sMessCounter: .asciz "sorted in @ flips \n" szCarriageReturn: .asciz "\n"
.align 4
- TableNumber: .int 1,11,3,6,2,5,9,10,8,4,7
TableNumber: .int 10,9,8,7,6,5,4,3,2,1
.equ NBELEMENTS, (. - TableNumber) / 4
/*********************************/ /* UnInitialized data */ /*********************************/ .bss sZoneConv: .skip 24 /*********************************/ /* code section */ /*********************************/ .text .global main main: @ entry of program
ldr r0,iAdrTableNumber @ address number table mov r1,#0 @ first element mov r2,#NBELEMENTS @ number of élements mov r10,#0 @ flips counter bl pancakeSort ldr r0,iAdrTableNumber @ address number table bl displayTable mov r0,r10 @ display counter ldr r1,iAdrsZoneConv @ bl conversion10S @ décimal conversion ldr r0,iAdrsMessCounter ldr r1,iAdrsZoneConv @ insert conversion bl strInsertAtCharInc bl affichageMess @ display message ldr r0,iAdrTableNumber @ address number table mov r1,#NBELEMENTS @ number of élements bl isSorted @ control sort cmp r0,#1 @ sorted ? beq 1f ldr r0,iAdrszMessSortNok @ no !! error sort bl affichageMess b 100f
1: @ yes
ldr r0,iAdrszMessSortOk bl affichageMess
100: @ standard end of the program
mov r0, #0 @ return code mov r7, #EXIT @ request to exit program svc #0 @ perform the system call
iAdrszCarriageReturn: .int szCarriageReturn iAdrsMessResult: .int sMessResult iAdrTableNumber: .int TableNumber iAdrszMessSortOk: .int szMessSortOk iAdrszMessSortNok: .int szMessSortNok iAdrsMessCounter: .int sMessCounter /******************************************************************/ /* control sorted table */ /******************************************************************/ /* r0 contains the address of table */ /* r1 contains the number of elements > 0 */ /* r0 return 0 if not sorted 1 if sorted */ isSorted:
push {r2-r4,lr} @ save registers
mov r2,#0
ldr r4,[r0,r2,lsl #2]
1:
add r2,#1 cmp r2,r1 movge r0,#1 bge 100f ldr r3,[r0,r2, lsl #2] cmp r3,r4 movlt r0,#0 blt 100f mov r4,r3 b 1b
100:
pop {r2-r4,lr}
bx lr @ return
/******************************************************************/ /* flip */ /******************************************************************/ /* r0 contains the address of table */ /* r1 contains first start index /* r2 contains the number of elements */ /* r3 contains the position of flip */ flip:
push {r1-r6,lr} @ save registers
add r10,r10,#1 @ flips counter
cmp r3,r2
subge r3,r2,#1 @ last index if position >= size
mov r4,r1
1:
cmp r1,r3 bge 100f ldr r5,[r0,r1,lsl #2] @ load value first index ldr r6,[r0,r3,lsl #2] @ load value position index str r6,[r0,r1,lsl #2] @ inversion str r5,[r0,r3,lsl #2] @ sub r3,r3,#1 add r1,r1,#1 b 1b
100:
pop {r1-r6,lr}
bx lr @ return
/******************************************************************/ /* pancake sort */ /******************************************************************/ /* r0 contains the address of table */ /* r1 contains first start index /* r2 contains the number of elements */ pancakeSort:
push {r1-r9,lr} @ save registers
sub r7,r2,#1
1:
mov r5,r1 @ index mov r4,#0 @ max mov r3,#0 @ position mov r8,#0 @ top sorted ldr r9,[r0,r5,lsl #2] @ load value A[i-1]
2:
ldr r6,[r0,r5,lsl #2] @ load value cmp r6,r4 @ compare max movge r4,r6 movge r3,r5 cmp r6,r9 @ cmp A[i] A[i-1] sorted ? movlt r8,#1 @ no mov r9,r6 @ A[i-1] = A[i] add r5,r5,#1 @ increment index cmp r5,r7 @ end ble 2b cmp r8,#0 @ sorted ? beq 100f @ yes -> end cmp r3,r7 @ position ok ? beq 3f @ yes cmp r3,#0 @ first position ? blne flip @ flip if not greather in first position mov r3,r7 @ and flip the whole stack bl flip @
3:
subs r7,r7,#1 @ decrement number of pancake bge 1b @ and loop
100:
pop {r1-r9,lr}
bx lr @ return
/******************************************************************/
/* Display table elements */
/******************************************************************/
/* r0 contains the address of table */
displayTable:
push {r0-r3,lr} @ save registers
mov r2,r0 @ table address
mov r3,#0
1: @ loop display table
ldr r0,[r2,r3,lsl #2] ldr r1,iAdrsZoneConv @ bl conversion10S @ décimal conversion ldr r0,iAdrsMessResult ldr r1,iAdrsZoneConv @ insert conversion bl strInsertAtCharInc bl affichageMess @ display message add r3,#1 cmp r3,#NBELEMENTS - 1 ble 1b ldr r0,iAdrszCarriageReturn bl affichageMess mov r0,r2
100:
pop {r0-r3,lr}
bx lr
iAdrsZoneConv: .int sZoneConv /***************************************************/ /* ROUTINES INCLUDE */ /***************************************************/ .include "../affichage.inc"
</lang>
Arturo
<lang rebol>pancakeSort: function [items][
arr: new items
len: size arr
loop (len-1)..1 'endIdx [
maxim: max slice arr 0 endIdx
maximIdx: index arr maxim
if maximIdx=endIdx -> continue
if maximIdx > 0 [
arr: (reverse slice arr 0 maximIdx) ++ slice arr maximIdx+1 (size arr)-1
]
arr: (reverse slice arr 0 endIdx) ++ slice arr endIdx+1 (size arr)-1 ] arr
]
print pancakeSort [3 1 2 8 5 7 9 4 6]</lang>
- Output:
1 2 3 4 5 6 7 8 9
AutoHotkey
<lang autohotkey>;--------------------------------------------------------------------------- Loop { ; test loop
- ---------------------------------------------------------------------------
Loop, % Data0 := 10
Random, Data%A_Index%, 10, 99
Unsorted := Array2List("Data")
PancakeSort("Data")
Sorted := Array2List("Data")
MsgBox, 1, Pancake Sort, %Unsorted%`n%Sorted%
IfMsgBox, Cancel, Break
}
- ---------------------------------------------------------------------------
PancakeSort(Array) { ; implementation of pancake sort algorithm
- ---------------------------------------------------------------------------
Loop, % %Array%0 - 1 {
m := 0
Loop, % s := %Array%0 - A_Index + 1
If (m <= %Array%%A_Index%)
m := %Array%%A_Index%, p := A_Index
If (p < s) && (p > 1)
Flip(Array, p)
If (p < s)
Flip(Array, s)
}
}
- ---------------------------------------------------------------------------
Flip(Array, n) { ; flip the first n members of Array
- ---------------------------------------------------------------------------
Loop, % x := n // 2 {
i := n - A_Index + 1
%Array%%i% := (%Array%%A_Index% "", %Array%%A_Index% := %Array%%i%)
}
}
- ---------------------------------------------------------------------------
Array2List(Array) { ; returns a space separated list from an array
- ---------------------------------------------------------------------------
Loop, % %Array%0
List .= (A_Index = 1 ? "" : " ") %Array%%A_Index%
Return, List
} </lang>
BASIC
Text
<lang qbasic>RANDOMIZE TIMER
DIM nums(9) AS INTEGER DIM L0 AS INTEGER, L1 AS INTEGER, n AS INTEGER
'initial values FOR L0 = 0 TO 9
nums(L0) = L0
NEXT 'scramble FOR L0 = 9 TO 1 STEP -1
n = INT(RND * (L0)) + 1 IF n <> L0 THEN SWAP nums(n), nums(L0)
NEXT 'display initial condition FOR L0 = 0 TO 9
PRINT nums(L0);
NEXT PRINT
FOR L1 = 9 TO 1 STEP -1
n = 0
FOR L0 = 1 TO L1
IF nums(n) < nums(L0) THEN n = L0
NEXT
IF (n < L1) THEN
IF (n > 0) THEN
FOR L0 = 0 TO (n \ 2)
SWAP nums(L0), nums(n - L0)
NEXT
FOR L0 = 0 TO 9
PRINT nums(L0);
NEXT
PRINT
END IF
FOR L0 = 0 TO (L1 \ 2)
SWAP nums(L0), nums(L1 - L0)
NEXT
FOR L0 = 0 TO 9
PRINT nums(L0);
NEXT
PRINT
END IF
NEXT</lang>
Sample output:
0 4 6 1 8 7 2 5 3 9 8 1 6 4 0 7 2 5 3 9 3 5 2 7 0 4 6 1 8 9 7 2 5 3 0 4 6 1 8 9 1 6 4 0 3 5 2 7 8 9 6 1 4 0 3 5 2 7 8 9 2 5 3 0 4 1 6 7 8 9 5 2 3 0 4 1 6 7 8 9 1 4 0 3 2 5 6 7 8 9 4 1 0 3 2 5 6 7 8 9 2 3 0 1 4 5 6 7 8 9 3 2 0 1 4 5 6 7 8 9 1 0 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
Graphics
This is a graphical variation of the above.
<lang qbasic>RANDOMIZE TIMER
CONST delay = .1 'controls display speed
DIM nums(14) AS INTEGER DIM L0 AS INTEGER, L1 AS INTEGER, n AS INTEGER, ttmp AS SINGLE
'initial values FOR L0 = 0 TO 14
nums(L0) = L0
NEXT 'scramble FOR L0 = 14 TO 1 STEP -1
n = INT(RND * (L0)) + 1 IF n <> L0 THEN SWAP nums(n), nums(L0)
NEXT
'display initial condition CLS GOSUB displayer
FOR L1 = 14 TO 1 STEP -1
n = 0
FOR L0 = 1 TO L1
IF nums(n) < nums(L0) THEN n = L0
NEXT
IF (n < L1) THEN
IF (n > 0) THEN
FOR L0 = 0 TO (n \ 2)
SWAP nums(L0), nums(n - L0)
NEXT
GOSUB displayer
END IF
FOR L0 = 0 TO (L1 \ 2)
SWAP nums(L0), nums(L1 - L0)
NEXT
GOSUB displayer END IF
NEXT
COLOR 7 END
displayer:
LOCATE 1, 1
FOR L0 = 0 TO 14
COLOR nums(L0) + 1
IF nums(L0) < 10 THEN PRINT " ";
PRINT RTRIM$(LTRIM$(STR$(nums(L0)))); STRING$(nums(L0), 219); SPACE$(20)
NEXT
ttmp = TIMER
DO WHILE TIMER < ttmp + delay: LOOP
RETURN</lang>
Sample output:
Batch File
<lang dos>:: Pancake Sort from Rosetta Code
- Batch File Implementation
@echo off setlocal enabledelayedexpansion
- put the input sequence of integers (only) on the list variable.
set "list=-2 0 -1 5 2 7 4 3 6 -1 7 2 1 8"
- create a pseudo-array; start at 0.
set "range=-1" for %%l in (%list%) do ( set /a "range+=1" set "num!range!=%%l" )
- scramble (remove this if you do not want to scramble the integers)
for /l %%l in (%range%,-1,1) do ( set /a "n=%random% %% %%l" rem swapping... for %%? in (num!n!) do set "swaptemp=!%%?!" set "num!n!=!num%%l!" set "num%%l=!swaptemp!" )
- display initial condition
set "output=" for /l %%l in (0,1,%range%) do set "output=!output! !num%%l!" echo(Initial Sequence: echo( echo( ^>^> %output% echo( echo(Sorting: echo(
- begin sort
for /l %%l in (%range%,-1,1) do ( set "n=0" for /l %%m in (1,1,%%l) do ( for %%? in (num!n!) do if !%%?! lss !num%%m! set "n=%%m" )
if !n! lss %%l ( if !n! gtr 0 ( set /a "tempvar1=!n!/2" %== corresponds to (n \ 2) from BASIC code ==% for /l %%m in (0,1,!tempvar1!) do ( set /a "tempvar2=!n!-%%m" %== corresponds to (n - L0) from BASIC code ==% rem swapping... for %%? in (num!tempvar2!) do set "swaptemp=!%%?!" set "num!tempvar2!=!num%%m!" set "num%%m=!swaptemp!" ) rem display the action set "output=" for /l %%x in (0,1,%range%) do set "output=!output! !num%%x!" echo( ^>^> !output! )
set /a "tempvar1=%%l/2" %== corresponds to (L1 \ 2) from BASIC code ==% for /l %%m in (0,1,!tempvar1!) do ( set /a "tempvar2=%%l-%%m" %== corresponds to (L1 - L0) from BASIC code ==% rem swapping... for %%? in (num!tempvar2!) do set "swaptemp=!%%?!" set "num!tempvar2!=!num%%m!" set "num%%m=!swaptemp!" ) rem display the action set output= for /l %%x in (0,1,%range%) do set "output=!output! !num%%x!" echo. ^>^> !output! ) )
)
echo DONE^^! exit /b 0</lang>
- Output:
Initial Sequence:
>> 8 3 5 6 -1 0 -2 2 -1 7 2 1 4 7
Sorting:
>> 7 4 1 2 7 -1 2 -2 0 -1 6 5 3 8
>> 3 5 6 -1 0 -2 2 -1 7 2 1 4 7 8
>> 7 -1 2 -2 0 -1 6 5 3 2 1 4 7 8
>> 4 1 2 3 5 6 -1 0 -2 2 -1 7 7 8
>> 6 5 3 2 1 4 -1 0 -2 2 -1 7 7 8
>> -1 2 -2 0 -1 4 1 2 3 5 6 7 7 8
>> 4 -1 0 -2 2 -1 1 2 3 5 6 7 7 8
>> 3 2 1 -1 2 -2 0 -1 4 5 6 7 7 8
>> -1 0 -2 2 -1 1 2 3 4 5 6 7 7 8
>> 2 -2 0 -1 -1 1 2 3 4 5 6 7 7 8
>> 2 1 -1 -1 0 -2 2 3 4 5 6 7 7 8
>> -2 0 -1 -1 1 2 2 3 4 5 6 7 7 8
>> 0 -2 -1 -1 1 2 2 3 4 5 6 7 7 8
>> -1 -1 -2 0 1 2 2 3 4 5 6 7 7 8
>> -2 -1 -1 0 1 2 2 3 4 5 6 7 7 8
DONE!
BBC BASIC
<lang bbcbasic> DIM test(9)
test() = 4, 65, 2, -31, 0, 99, 2, 83, 782, 1
PROCpancakesort(test())
FOR i% = 0 TO 9
PRINT test(i%) ;
NEXT
PRINT
END
DEF PROCpancakesort(a())
LOCAL i%, j%, m%
FOR i% = DIM(a(),1)+1 TO 2 STEP -1
m% = 0
FOR j% = 1 TO i%-1
IF a(j%) > a(m%) m% = j%
NEXT
m% += 1
IF m% < i% THEN
IF m% > 1 PROCflip(a(), m%)
PROCflip(a(), i%)
ENDIF
NEXT
ENDPROC
DEF PROCflip(a(), n%)
IF n% < 2 ENDPROC
LOCAL i%
n% -= 1
FOR i% = 0 TO n% DIV 2
SWAP a(i%), a(n%-i%)
NEXT
ENDPROC</lang>
Output:
-31 0 1 2 2 4 65 83 99 782
C
The function that sorts: <lang c>int pancake_sort(int *list, unsigned int length) {
//If it's less than 2 long, just return it as sorting isn't really needed...
if(length<2)
return 0;
int i,a,max_num_pos,moves; moves=0;
for(i=length;i>1;i--)
{
//Find position of the max number in pos(0) to pos(i)
max_num_pos=0;
for(a=0;a<i;a++)
{
if(list[a]>list[max_num_pos])
max_num_pos=a;
}
if(max_num_pos==i-1)
//It's where it need to be, skip
continue;
//Get the found max number to the beginning of the list (unless it already is)
if(max_num_pos)
{
moves++;
do_flip(list, length, max_num_pos+1);
}
//And then move it to the end of the range we're working with (pos(0) to pos(i))
moves++;
do_flip(list, length, i);
//Then everything above list[i-1] is sorted and don't need to be touched
}
return moves;
}</lang>
Where do_flip() is a simple function to flip a part of an array: <lang c>void do_flip(int *list, int length, int num) {
int swap;
int i=0;
for(i;i<--num;i++)
{
swap=list[i];
list[i]=list[num];
list[num]=swap;
}
}</lang>
Testing the function: <lang c>int main(int argc, char **argv) {
//Just need some random numbers. I chose <100
int list[9];
int i;
srand(time(NULL));
for(i=0;i<9;i++)
list[i]=rand()%100;
//Print list, run code and print it again displaying number of moves
printf("\nOriginal: ");
print_array(list, 9);
int moves = pancake_sort(list, 9, 1);
printf("\nSorted: ");
print_array(list, 9);
printf(" - with a total of %d moves\n", moves);
}</lang>
C#
<lang C sharp|C#> public static class PancakeSorter {
public static void Sort<T>(List<T> list) where T : IComparable
{
if (list.Count < 2)
{
return;
}
int i, a, max_num_pos;
for (i = list.Count; i > 1; i--)
{
max_num_pos = 0;
for (a = 0; a < i; a++)
{
if (list[a].CompareTo(list[max_num_pos]) > 0)
{
max_num_pos = a;
}
}
if (max_num_pos == i - 1)
{
continue;
}
if (max_num_pos > 0)
{
Flip(list, list.Count, max_num_pos + 1);
}
Flip(list, list.Count, i);
}
return;
}
private static void Flip<T>(List<T> list, int length, int num)
{
for (int i = 0; i < --num; i++)
{
T swap = list[i];
list[i] = list[num];
list[num] = swap;
}
}
} </lang>
C++
<lang c>#include <algorithm>
- include <iostream>
- include <iterator>
- include <vector>
// pancake sort template (calls predicate to determine order) template <typename BidIt, typename Pred> void pancake_sort(BidIt first, BidIt last, Pred order) {
if (std::distance(first, last) < 2) return; // no sort needed
for (; first != last; --last)
{
BidIt mid = std::max_element(first, last, order);
if (mid == last - 1)
{
continue; // no flips needed
}
if (first != mid)
{
std::reverse(first, mid + 1); // flip element to front
}
std::reverse(first, last); // flip front to final position
}
}
// pancake sort template (ascending order) template <typename BidIt> void pancake_sort(BidIt first, BidIt last) {
pancake_sort(first, last, std::less<typename std::iterator_traits<BidIt>::value_type>());
}
int main() {
std::vector<int> data;
for (int i = 0; i < 20; ++i)
{
data.push_back(i); // generate test data
}
std::random_shuffle(data.begin(), data.end()); // scramble data
std::copy(data.begin(), data.end(), std::ostream_iterator<int>(std::cout, " ")); std::cout << "\n";
pancake_sort(data.begin(), data.end()); // ascending pancake sort
std::copy(data.begin(), data.end(), std::ostream_iterator<int>(std::cout, " ")); std::cout << "\n";
}</lang>Output:
4 10 11 15 14 16 17 1 6 9 3 7 19 2 0 12 5 18 13 8 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Clojure
<lang clojure> (defn pancake-sort
[arr]
(if (= 1 (count arr))
arr
(when-let [mx (apply max arr)]
(let [tk (split-with #(not= mx %) arr)
tail (second tk)
torev (concat (first tk) (take 1 tail))
head (reverse torev)]
(cons mx (pancake-sort (concat (drop 1 head) (drop 1 tail))))))))
</lang>
Common Lisp
<lang lisp>(defun pancake-sort (seq)
"A destructive version of Pancake Sort that works with either lists or arrays of numbers." (defun flip (lst index) (setf (subseq lst 0 index) (reverse (subseq lst 0 index)))) (loop with lst = (coerce seq 'list)
for i from (length lst) downto 2 for index = (position (apply #'max (subseq lst 0 i)) lst) do (unless (= index 0) (flip lst (1+ index))) (flip lst i) finally (return (coerce lst (type-of seq)))))</lang> Output: <lang lisp>CL-USER> (pancake-sort '(6 7 8 9 2 5 3 4 1)) ;list (1 2 3 4 5 6 7 8 9) CL-USER> (pancake-sort #(6 7 8 9 2 5 3 4 1)) ;array
- (1 2 3 4 5 6 7 8 9)
CL-USER> (pancake-sort #(6.5 7.5 8 9 2 5 3 4 1.0)) ;array with integer and floating point values
- (1.0 2 3 4 5 6.5 7.5 8 9)</lang>
D
<lang d>import std.stdio, std.algorithm;
void pancakeSort(bool tutor=false, T)(T[] data) {
foreach_reverse (immutable i; 2 .. data.length + 1) {
immutable maxIndex = i - data[0 .. i].minPos!q{a > b}.length;
if (maxIndex + 1 != i) {
if (maxIndex != 0) {
static if (tutor)
writeln("With: ", data, " doflip ", maxIndex + 1);
data[0 .. maxIndex + 1].reverse();
}
static if (tutor)
writeln("With: ", data, " doflip ", i);
data[0 .. i].reverse();
}
}
}
void main() {
auto data = "769248135".dup; data.pancakeSort!true; data.writeln;
}</lang>
- Output:
With: 769248135 doflip 3 With: 967248135 doflip 9 With: 531842769 doflip 4 With: 813542769 doflip 8 With: 672453189 doflip 2 With: 762453189 doflip 7 With: 135426789 doflip 3 With: 531426789 doflip 5 With: 241356789 doflip 2 With: 421356789 doflip 4 With: 312456789 doflip 3 With: 213456789 doflip 2 123456789
Eiffel
<lang Eiffel> class PANCAKE_SORT [G -> COMPARABLE]
feature {NONE}
arraymax (array: ARRAY [G]; upper: INTEGER): INTEGER --- Max item of 'array' between index 1 and 'upper'. require upper_index_positive: upper >= 0 array_not_void: array /= Void local i: INTEGER cur_max: G do from i := 1 cur_max := array.item (i) Result := i until i + 1 > upper loop if array.item (i + 1) > cur_max then cur_max := array.item (i + 1) Result := i + 1 end i := i + 1 end ensure Index_positive: Result > 0 end
reverse_array (ar: ARRAY [G]; upper: INTEGER): ARRAY [G] -- Array reversed from index one to upper. require upper_positive: upper > 0 ar_not_void: ar /= Void local i, j: INTEGER new_array: ARRAY [G] do create Result.make_empty Result.deep_copy (ar) from i := 1 j := upper until i > j loop Result [i] := ar [j] Result [j] := ar [i] i := i + 1 j := j - 1 end ensure same_length: ar.count = Result.count end
sort (ar: ARRAY [G]): ARRAY [G] -- Sorted array in ascending order. local i: INTEGER do create Result.make_empty Result.deep_copy (ar) from i := ar.count until i = 1 loop Result := reverse_array (reverse_array (Result, arraymax (Result, i)), i) i := i - 1 end ensure same_length: ar.count = Result.count Result_sorted: is_sorted (Result) end
is_sorted (ar: ARRAY [G]): BOOLEAN --- Is 'ar' sorted in ascending order? require ar_not_empty: ar.is_empty = False local i: INTEGER do Result := True from i := ar.lower until i = ar.upper loop if ar [i] > ar [i + 1] then Result := False end i := i + 1 end end
feature
pancake_sort (ar: ARRAY [G]): ARRAY [G] do Result := sort (ar) end
end </lang>
Test: <lang Eiffel> class APPLICATION
create make
feature
make do test := <<1, 27, 32, 99, 1, -7, 3, 5>> create sorter io.put_string ("Unsorted: ") across test as ar loop io.put_string (ar.item.out + " ") end io.put_string ("%NSorted: ") test := sorter.pancake_sort(test) across test as ar loop io.put_string (ar.item.out + " ") end end
test: ARRAY [INTEGER]
sorter: PANCAKE_SORT[INTEGER]
end </lang>
- Output:
Unsorted: 1 27 32 99 1 -7 3 5 Sorted: -7 1 1 3 5 27 32 99
Elena
ELENA 5.0 :
<lang elena>import extensions;
extension op {
pancakeSort()
{
var list := self.clone();
int i := list.Length;
if (i < 2) { ^ self };
while (i > 1)
{
int max_num_pos := 0;
int a := 0;
while (a < i)
{
if (list[a] > list[max_num_pos])
{
max_num_pos := a
};
a += 1
};
if (max_num_pos == i - 1)
{
}
else
{
if (max_num_pos > 0)
{
list.flip(list.Length, max_num_pos + 1)
};
list.flip(list.Length, i)
};
i -= 1
};
^ list
}
flip(int length, int num)
{
int i := 0;
int count := num - 1;
while (i < count)
{
var swap := self[i];
self[i] := self[count];
self[count] := swap;
i += 1;
count -= 1
}
}
}
public program() {
var list := new int[]{6, 7, 8, 9, 2, 5, 3, 4, 1};
console.printLine("before:", list.asEnumerable());
console.printLine("after :", list.pancakeSort().asEnumerable())
}</lang>
- Output:
before:6,7,8,9,2,5,3,4,1 after :1,2,3,4,5,6,7,8,9
Elixir
<lang elixir>defmodule Sort do
def pancake_sort(list) when is_list(list), do: pancake_sort(list, length(list))
defp pancake_sort(list, 0), do: list
defp pancake_sort(list, limit) do
index = search_max(list, limit)
flip(list, index) |> flip(limit) |> pancake_sort(limit-1)
end
defp search_max([h | t], limit), do: search_max(t, limit, 2, h, 1)
defp search_max(_, limit, index, _, max_index) when limit<index, do: max_index
defp search_max([h | t], limit, index, max, max_index) do
if h > max, do: search_max(t, limit, index+1, h, index),
else: search_max(t, limit, index+1, max, max_index)
end
defp flip(list, n), do: flip(list, n, [])
defp flip(list, 0, reverse), do: reverse ++ list
defp flip([h | t], n, reverse) do
flip(t, n-1, [h | reverse])
end
end
IO.inspect list = Enum.shuffle(1..9) IO.inspect Sort.pancake_sort(list)</lang>
- Output:
[3, 7, 2, 8, 6, 4, 9, 1, 5] [1, 2, 3, 4, 5, 6, 7, 8, 9]
Euphoria
<lang euphoria>function flip(sequence s, integer n)
object temp
for i = 1 to n/2 do
temp = s[i]
s[i] = s[n-i+1]
s[n-i+1] = temp
end for
return s
end function
function pancake_sort(sequence s)
integer m
for i = length(s) to 2 by -1 do
m = 1
for j = 2 to i do
if compare(s[j], s[m]) > 0 then
m = j
end if
end for
if m < i then
if m > 1 then
s = flip(s,m)
end if
s = flip(s,i)
end if
end for
return s
end function
constant s = rand(repeat(100,10))
? s ? pancake_sort(s)</lang>
Output:
{24,32,100,15,8,34,50,79,46,52}
{8,15,24,32,34,46,50,52,79,100}
F#
<lang fsharp>open System
let show data = data |> Array.iter (printf "%d ") ; printfn "" let split (data: int[]) pos = data.[0..pos], data.[(pos+1)..]
let flip items pos =
let lower, upper = split items pos Array.append (Array.rev lower) upper
let pancakeSort items =
let rec loop data limit =
if limit <= 0 then data
else
let lower, upper = split data limit
let indexOfMax = lower |> Array.findIndex ((=) (Array.max lower))
let partialSort = Array.append (flip lower indexOfMax |> Array.rev) upper
loop partialSort (limit-1)
loop items ((Array.length items)-1)</lang>
Usage: pancakeSort [|31; 41; 59; 26; 53; 58; 97; 93; 23; 84|] |> show
Output:
23 26 31 41 53 58 59 84 93 97
Fortran
<lang fortran>program Pancake_Demo
implicit none integer :: list(8) = (/ 1, 4, 7, 2, 5, 8, 3, 6 /) call Pancake_sort(list)
contains
subroutine Pancake_sort(a)
integer, intent(in out) :: a(:)
integer :: i, maxpos
write(*,*) a
do i = size(a), 2, -1
! Find position of max number between index 1 and i
maxpos = maxloc(a(1:i), 1)
! is it in the correct position already?
if (maxpos == i) cycle
! is it at the beginning of the array? If not flip array section so it is
if (maxpos /= 1) then
a(1:maxpos) = a(maxpos:1:-1)
write(*,*) a
end if
! Flip array section to get max number to correct position
a(1:i) = a(i:1:-1) write(*,*) a end do
end subroutine
end program Pancake_Demo</lang> Output:
1 4 7 2 5 8 3 6
8 5 2 7 4 1 3 6
6 3 1 4 7 2 5 8
7 4 1 3 6 2 5 8
5 2 6 3 1 4 7 8
6 2 5 3 1 4 7 8
4 1 3 5 2 6 7 8
5 3 1 4 2 6 7 8
2 4 1 3 5 6 7 8
4 2 1 3 5 6 7 8
3 1 2 4 5 6 7 8
2 1 3 4 5 6 7 8
1 2 3 4 5 6 7 8
FreeBASIC
<lang freebasic>' version 11-04-2017 ' compile with: fbc -s console ' for boundry checks on array's compile with: fbc -s console -exx
' direction = 1, (default) sort ascending ' direction <> 1 sort descending ' show = 0, (default) do not show sorting ' show <> 0, show sorting Sub pancake_sort(a() As Long,direction As Long = 1, show As Long = 0)
' array's can have subscript range from -2147483648 to +2147483647 Dim As Long i, j, n Dim As Long lb = LBound(a) Dim As Long ub = UBound(a)
If show <> 0 Then ' show initial state
For j = lb To ub
Print Using "####"; a(j);
Next
Print
End If
For i = ub To lb +1 Step -1
n = lb
For j = lb +1 To i
If direction = 1 Then
If a(n) < a(j) Then n = j
Else
If a(n) > a(j) Then n = j
End If
Next
If n < i Then
If n > lb Then
For j = lb To lb + ((n - lb) \ 2)
Swap a(j), a(lb + n - j)
Next
If show <> 0 Then
For j = lb To ub
Print Using "####"; a(j);
Next
Print
End If
End If
For j = lb To lb + ((i - lb) \ 2)
Swap a(j), a(lb + i - j)
Next
If show <> 0 Then
For j = lb To ub
Print Using "####"; a(j);
Next
Print
End If
End If Next
End Sub
' ------=< MAIN >=------
Dim As Long i, array(-7 To 7) Dim As Long lb = LBound(array) Dim As Long ub = UBound(array)
Randomize Timer For i = lb To ub : array(i) = i : Next For i = lb To ub ' little shuffle
Swap array(i), array(Int(Rnd * (ub - lb +1) + lb))
Next
Print "unsorted "; For i = lb To ub
Print Using "####"; array(i);
Next Print : Print
pancake_sort(array())
Print " sorted "; For i = lb To ub
Print Using "####"; array(i);
Next
Print : Print Dim As Long l(10 To ...) = {0, -30, 20, -10, 0, 10, -20}
pancake_sort(l(),0,1) ' sort array l, ascending and show process
Print : Print " sorted l()"; For i = LBound(l) To UBound(l)
Print Using "####"; l(i);
Next Print
' empty keyboard buffer While Inkey <> "" : Wend Print : Print "hit any key to end program" Sleep End</lang>
- Output:
unsorted -1 -4 1 6 7 5 2 -3 4 -5 -2 -6 0 3 -7 sorted -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 0 -30 20 -10 0 10 -20 -30 0 20 -10 0 10 -20 -20 10 0 -10 20 0 -30 0 20 -10 0 10 -20 -30 -10 20 0 0 10 -20 -30 10 0 0 20 -10 -20 -30 0 10 0 20 -10 -20 -30 20 0 10 0 -10 -20 -30 0 20 10 0 -10 -20 -30 10 20 0 0 -10 -20 -30 20 10 0 0 -10 -20 -30 sorted l() 20 10 0 0 -10 -20 -30
Go
<lang go>package main
import "fmt"
func main() {
list := pancake{31, 41, 59, 26, 53, 58, 97, 93, 23, 84}
fmt.Println("unsorted:", list)
list.sort()
fmt.Println("sorted! ", list)
}
type pancake []int
func (a pancake) sort() {
for uns := len(a) - 1; uns > 0; uns-- {
// find largest in unsorted range
lx, lg := 0, a[0]
for i := 1; i <= uns; i++ {
if a[i] > lg {
lx, lg = i, a[i]
}
}
// move to final position in two flips
a.flip(lx)
a.flip(uns)
}
}
func (a pancake) flip(r int) {
for l := 0; l < r; l, r = l+1, r-1 {
a[l], a[r] = a[r], a[l]
}
}</lang> Output:
unsorted: [31 41 59 26 53 58 97 93 23 84] sorted! [23 26 31 41 53 58 59 84 93 97]
Groovy
This formulation of the pancake sort achieves stability by picking the last index (rather than, say, the first) in the remaining sublist that matches the max value of the remaining sublist. Performance is enhanced somewhat by not flipping if the flipPoint is already at the end of the remaining sublist. <lang groovy>def makeSwap = { a, i, j = i+1 -> print "."; aj,i = ai,j }
def flip = { list, n -> (0..<((n+1)/2)).each { makeSwap(list, it, n-it) } }
def pancakeSort = { list ->
def n = list.size()
(1..<n).reverse().each { i ->
def max = list[0..i].max()
def flipPoint = (i..0).find{ list[it] == max }
if (flipPoint != i) {
flip(list, flipPoint)
flip(list, i)
}
}
list
}</lang>
Test: <lang groovy>println (pancakeSort([23,76,99,58,97,57,35,89,51,38,95,92,24,46,31,24,14,12,57,78,4])) println (pancakeSort([88,18,31,44,4,0,8,81,14,78,20,76,84,33,73,75,82,5,62,70,12,7,1])) println () println (pancakeSort([10, 10.0, 10.00, 1])) println (pancakeSort([10, 10.00, 10.0, 1])) println (pancakeSort([10.0, 10, 10.00, 1])) println (pancakeSort([10.0, 10.00, 10, 1])) println (pancakeSort([10.00, 10, 10.0, 1])) println (pancakeSort([10.00, 10.0, 10, 1]))</lang> The use of decimals and integers that compare as equal demonstrates, but of course not prove, that the sort is stable.
Output:
..........................................................................................................................................[4, 12, 14, 23, 24, 24, 31, 35, 38, 46, 51, 57, 57, 58, 76, 78, 89, 92, 95, 97, 99] ............................................................................................................................................................................................................[0, 1, 4, 5, 7, 8, 12, 14, 18, 20, 31, 33, 44, 62, 70, 73, 75, 76, 78, 81, 82, 84, 88] ...[1, 10, 10.0, 10.00] ...[1, 10, 10.00, 10.0] ...[1, 10.0, 10, 10.00] ...[1, 10.0, 10.00, 10] ...[1, 10.00, 10, 10.0] ...[1, 10.00, 10.0, 10]
Haskell
<lang haskell>import Data.List import Control.Arrow import Control.Monad import Data.Maybe
dblflipIt :: (Ord a) => [a] -> [a] dblflipIt = uncurry ((reverse.).(++)). first reverse
. ap (flip splitAt) (succ. fromJust. (elemIndex =<< maximum))
dopancakeSort :: (Ord a) => [a] -> [a] dopancakeSort xs = dopcs (xs,[]) where
dopcs ([],rs) = rs dopcs ([x],rs) = x:rs dopcs (xs,rs) = dopcs $ (init &&& (:rs).last ) $ dblflipIt xs</lang>
Example: <lang haskell>*Main> dopancakeSort [3,2,1,0,2] [0,1,2,2,3]</lang>
Haxe
<lang haxe>class PancakeSort {
@:generic
inline private static function flip<T>(arr:Array<T>, num:Int) {
var i = 0;
while (i < --num) {
var temp = arr[i];
arr[i++] = arr[num];
arr[num] = temp;
}
}
@:generic
public static function sort<T>(arr:Array<T>) {
if (arr.length < 2) return;
var i = arr.length;
while (i > 1) {
var maxNumPos = 0;
for (a in 0...i) {
if (Reflect.compare(arr[a], arr[maxNumPos]) > 0)
maxNumPos = a;
}
if (maxNumPos == i - 1) i--;
if (maxNumPos > 0) flip(arr, maxNumPos + 1);
flip(arr, i--);
}
}
}
class Main {
static function main() {
var integerArray = [1, 10, 2, 5, -1, 5, -19, 4, 23, 0];
var floatArray = [1.0, -3.2, 5.2, 10.8, -5.7, 7.3,
3.5, 0.0, -4.1, -9.5];
var stringArray = ['We', 'hold', 'these', 'truths', 'to',
'be', 'self-evident', 'that', 'all',
'men', 'are', 'created', 'equal'];
Sys.println('Unsorted Integers: ' + integerArray);
PancakeSort.sort(integerArray);
Sys.println('Sorted Integers: ' + integerArray);
Sys.println('Unsorted Floats: ' + floatArray);
PancakeSort.sort(floatArray);
Sys.println('Sorted Floats: ' + floatArray);
Sys.println('Unsorted Strings: ' + stringArray);
PancakeSort.sort(stringArray);
Sys.println('Sorted Strings: ' + stringArray);
}
}</lang>
- Output:
Unsorted Integers: [1,10,2,5,-1,5,-19,4,23,0] Sorted Integers: [-19,-1,0,1,2,4,5,5,10,23] Unsorted Floats: [1,-3.2,5.2,10.8,-5.7,7.3,3.5,0,-4.1,-9.5] Sorted Floats: [-9.5,-5.7,-4.1,-3.2,0,1,3.5,5.2,7.3,10.8] Unsorted Strings: [We,hold,these,truths,to,be,self-evident,that,all,men,are,created,equal] Sorted Strings: [We,all,are,be,created,equal,men,self-evident,hold,that,these,to,truths]
Icon and Unicon
<lang Icon>procedure main() #: demonstrate various ways to sort a list and string
demosort(pancakesort,[3, 14, 1, 5, 9, 2, 6, 3],"qwerty") pancakeflip := pancakeflipshow # replace pancakeflip procedure with a variant that displays each flip pancakesort([3, 14, 1, 5, 9, 2, 6, 3])
end
procedure pancakesort(X,op) #: return sorted list ascending(or descending) local i,m
op := sortop(op,X) # select how and what we sort
every i := *X to 2 by -1 do { # work back to front
m := 1
every j := 2 to i do
if op(X[m],X[j]) then m := j # find X that belongs @i high (or low)
if i ~= m then { # not already in-place
X := pancakeflip(X,m) # . bring max (min) to front
X := pancakeflip(X,i) # . unsorted portion of stack
}
}
return X
end
procedure pancakeflip(X,tail) #: return X[1:tail] flipped local i
i := 0 tail := integer(\tail|*X) + 1 | runerr(101,tail) while X[(i +:= 1) < (tail -:= 1)] :=: X[i] # flip return X
end
procedure pancakeflipshow(X,tail) #: return X[1:tail] flipped (and display) local i
i := 0
tail := integer(\tail|*X) + 1 | runerr(101,tail)
while X[(i +:= 1) < (tail -:= 1)] :=: X[i] # flip
every writes(" ["|right(!X,4)|" ]\n") # show X
return X
end</lang>
Note: This example relies on the supporting procedures 'sortop', and 'demosort' in Bubble Sort. The full demosort exercises the named sort of a list with op = "numeric", "string", ">>" (lexically gt, descending),">" (numerically gt, descending), a custom comparator, and also a string.
Abbreviated sample output:
Sorting Demo using procedure pancakesort
on list : [ 3 14 1 5 9 2 6 3 ]
with op = &null: [ 1 2 3 3 5 6 9 14 ] (0 ms)
...
on string : "qwerty"
with op = &null: "eqrtwy" (0 ms)The output below shows the flipping:
[ 14 3 1 5 9 2 6 3 ]
[ 3 6 2 9 5 1 3 14 ]
[ 9 2 6 3 5 1 3 14 ]
[ 3 1 5 3 6 2 9 14 ]
[ 6 3 5 1 3 2 9 14 ]
[ 2 3 1 5 3 6 9 14 ]
[ 5 1 3 2 3 6 9 14 ]
[ 3 2 3 1 5 6 9 14 ]
[ 3 2 3 1 5 6 9 14 ]
[ 1 3 2 3 5 6 9 14 ]
[ 3 1 2 3 5 6 9 14 ]
[ 2 1 3 3 5 6 9 14 ]
[ 2 1 3 3 5 6 9 14 ]
[ 1 2 3 3 5 6 9 14 ]
J
<lang J>flip=: C.~ C.@i.@- unsorted=: #~ 1 , [: >./\. 2 >/\ ] FlDown=: flip 1 + (i. >./)@unsorted FlipUp=: flip 1 >. [:+/>./\&|.@(< {.)
pancake=: FlipUp@FlDown^:_</lang>
Example use:
<lang J> (,:pancake) ?~9 1 0 8 7 4 6 3 5 2 0 1 2 3 4 5 6 7 8</lang>
See the discussion page for illustrations of the other words.
Java
<lang java> public class PancakeSort {
int[] heap;
public String toString() {
String info = "";
for (int x: heap)
info += x + " ";
return info;
}
public void flip(int n) {
for (int i = 0; i < (n+1) / 2; ++i) {
int tmp = heap[i];
heap[i] = heap[n-i];
heap[n-i] = tmp;
}
System.out.println("flip(0.." + n + "): " + toString());
}
public int[] minmax(int n) {
int xm, xM;
xm = xM = heap[0];
int posm = 0, posM = 0;
for (int i = 1; i < n; ++i) {
if (heap[i] < xm) {
xm = heap[i];
posm = i;
}
else if (heap[i] > xM) {
xM = heap[i];
posM = i;
}
}
return new int[] {posm, posM};
}
public void sort(int n, int dir) {
if (n == 0) return;
int[] mM = minmax(n);
int bestXPos = mM[dir];
int altXPos = mM[1-dir];
boolean flipped = false;
if (bestXPos == n-1) {
--n;
}
else if (bestXPos == 0) {
flip(n-1);
--n;
}
else if (altXPos == n-1) {
dir = 1-dir;
--n;
flipped = true;
}
else {
flip(bestXPos);
}
sort(n, dir);
if (flipped) {
flip(n);
}
}
PancakeSort(int[] numbers) {
heap = numbers;
sort(numbers.length, 1);
}
public static void main(String[] args) {
int[] numbers = new int[args.length];
for (int i = 0; i < args.length; ++i)
numbers[i] = Integer.valueOf(args[i]);
PancakeSort pancakes = new PancakeSort(numbers);
System.out.println(pancakes);
}
}</lang>
Example: <lang bash>$ java PancakeSort 1 2 5 4 3 10 9 8 7 flip(0..5): 10 3 4 5 2 1 9 8 7 flip(0..8): 7 8 9 1 2 5 4 3 10 flip(0..2): 9 8 7 1 2 5 4 3 10 flip(0..7): 3 4 5 2 1 7 8 9 10 flip(0..2): 5 4 3 2 1 7 8 9 10 flip(0..4): 1 2 3 4 5 7 8 9 10 1 2 3 4 5 7 8 9 10
$ java PancakeSort 6 7 2 1 8 9 5 3 4 flip(0..5): 9 8 1 2 7 6 5 3 4 flip(0..8): 4 3 5 6 7 2 1 8 9 flip(0..1): 3 4 5 6 7 2 1 8 9 flip(0..4): 7 6 5 4 3 2 1 8 9 flip(0..6): 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 </lang>
JavaScript
<lang javascript>Array.prototype.pancake_sort = function () {
for (var i = this.length - 1; i >= 1; i--) {
// find the index of the largest element not yet sorted
var max_idx = 0;
var max = this[0];
for (var j = 1; j <= i; j++) {
if (this[j] > max) {
max = this[j];
max_idx = j;
}
}
if (max_idx == i)
continue; // element already in place
var new_slice;
// flip this max element to index 0
if (max_idx > 0) {
new_slice = this.slice(0, max_idx+1).reverse();
for (var j = 0; j <= max_idx; j++)
this[j] = new_slice[j];
}
// then flip the max element to its place
new_slice = this.slice(0, i+1).reverse();
for (var j = 0; j <= i; j++)
this[j] = new_slice[j];
}
return this;
} ary = [7,6,5,9,8,4,3,1,2,0] sorted = ary.concat().pancake_sort();</lang>
jq
This version skips the pair of flips if the focal item is already in place. <lang jq>def pancakeSort:
def flip(i): . as $in | ($in[0:i+1]|reverse) + $in[i+1:] ;
# If input is [] then return null
def index_of_max:
. as $in
| reduce range(1; length) as $i
# state: [ix, max]
( [ 0, $in[0] ];
if $in[$i] > .[1] then [ $i, $in[$i] ] else . end )
| .[0] ;
reduce range(0; length) as $iup
(.;
(length - $iup - 1) as $i
| (.[0:$i+1] | index_of_max) as $max
# flip about $max and then about $i unless $i == $max
| if ($i == $max) then .
else flip($max) | flip($i)
end ) ;</lang>
Example: <lang jq>[range(0;2), null, 1.0, 0.5, [1], [2], {"b":1}, {"a":2}, range(2;4)]
| pancakeSort</lang>
- Output:
<lang sh>$ jq -M -c -n -f pancake_sort.jq [null,0,0.5,1,1,2,3,[1],[2],{"a":2},{"b":1}]</lang>
Julia
<lang julia>function pancakesort!(arr::Vector{<:Real})
len = length(arr)
if len < 2 return arr end
for i in len:-1:2
j = indmax(arr[1:i])
if i == j continue end
arr[1:j] = reverse(arr[1:j])
arr[1:i] = reverse(arr[1:i])
end
return arr
end
v = rand(-10:10, 10) println("# unordered: $v\n -> ordered: ", pancakesort!(v))</lang>
- Output:
# unordered: [0, -9, -8, 2, -7, 8, 6, -2, -8, 3] -> ordered: [-9, -8, -8, -7, -2, 0, 2, 3, 6, 8]
Kotlin
<lang kotlin>fun pancakeSort(a: IntArray) {
/** Returns the index of the highest number in the range 0 until n. */
fun indexOfMax(n: Int): Int = (0 until n).maxByOrNull{ a[it] }!!
/** Flips the elements in the range 0 .. n. */
fun flip(index: Int) {
a.reverse(0, index + 1)
}
for (n in a.size downTo 2) { // successively reduce size of array by 1
val index = indexOfMax(n) // find index of largest
if (index != n - 1) { // if it's not already at the end
if (index > 0) { // if it's not already at the beginning
flip(index) // move largest to beginning
println("${a.contentToString()} after flipping first ${index + 1}")
}
flip(n - 1) // move largest to end
println("${a.contentToString()} after flipping first $n")
}
}
}
fun main() {
val a = intArrayOf(7, 6, 9, 2, 4, 8, 1, 3, 5)
println("${a.contentToString()} initially")
pancakeSort(a)
}</lang>
- Output:
[7, 6, 9, 2, 4, 8, 1, 3, 5] initially [9, 6, 7, 2, 4, 8, 1, 3, 5] after flipping first 3 [5, 3, 1, 8, 4, 2, 7, 6, 9] after flipping first 9 [8, 1, 3, 5, 4, 2, 7, 6, 9] after flipping first 4 [6, 7, 2, 4, 5, 3, 1, 8, 9] after flipping first 8 [7, 6, 2, 4, 5, 3, 1, 8, 9] after flipping first 2 [1, 3, 5, 4, 2, 6, 7, 8, 9] after flipping first 7 [5, 3, 1, 4, 2, 6, 7, 8, 9] after flipping first 3 [2, 4, 1, 3, 5, 6, 7, 8, 9] after flipping first 5 [4, 2, 1, 3, 5, 6, 7, 8, 9] after flipping first 2 [3, 1, 2, 4, 5, 6, 7, 8, 9] after flipping first 4 [2, 1, 3, 4, 5, 6, 7, 8, 9] after flipping first 3 [1, 2, 3, 4, 5, 6, 7, 8, 9] after flipping first 2
Lua
<lang Lua>-- Initialisation math.randomseed(os.time()) numList = {step = 0, sorted = 0}
-- Create list of n random values function numList:build (n)
self.values = {}
for i = 1, n do self.values[i] = math.random(-100, 100) end
end
-- Return boolean indicating whether the list is in order function numList:isSorted ()
for i = 2, #self.values do
if self.values[i] < self.values[i - 1] then return false end
end
print("Finished!")
return true
end
-- Display list of numbers on one line function numList:show ()
if self.step == 0 then
io.write("Initial state:\t")
else
io.write("After step " .. self.step .. ":\t")
end
for _, v in ipairs(self.values) do io.write(v .. " ") end
print()
end
-- Reverse n values from the left function numList:reverse (n)
local flipped = {}
for i, v in ipairs(self.values) do
if i > n then
flipped[i] = v
else
flipped[i] = self.values[n + 1 - i]
end
end
self.values = flipped
end
-- Perform one flip of a pancake sort function numList:pancake ()
local maxPos = 1
for i = 1, #self.values - self.sorted do
if self.values[i] > self.values[maxPos] then maxPos = i end
end
if maxPos == 1 then
numList:reverse(#self.values - self.sorted)
self.sorted = self.sorted + 1
else
numList:reverse(maxPos)
end
self.step = self.step + 1
end
-- Main procedure numList:build(10) numList:show() repeat
numList:pancake() numList:show()
until numList:isSorted() </lang>
- Output:
Initial state: -67 61 80 47 21 74 43 22 66 -66 After step 1: 80 61 -67 47 21 74 43 22 66 -66 After step 2: -66 66 22 43 74 21 47 -67 61 80 After step 3: 74 43 22 66 -66 21 47 -67 61 80 After step 4: 61 -67 47 21 -66 66 22 43 74 80 After step 5: 66 -66 21 47 -67 61 22 43 74 80 After step 6: 43 22 61 -67 47 21 -66 66 74 80 After step 7: 61 22 43 -67 47 21 -66 66 74 80 After step 8: -66 21 47 -67 43 22 61 66 74 80 After step 9: 47 21 -66 -67 43 22 61 66 74 80 After step 10: 22 43 -67 -66 21 47 61 66 74 80 After step 11: 43 22 -67 -66 21 47 61 66 74 80 After step 12: 21 -66 -67 22 43 47 61 66 74 80 After step 13: 22 -67 -66 21 43 47 61 66 74 80 After step 14: 21 -66 -67 22 43 47 61 66 74 80 After step 15: -67 -66 21 22 43 47 61 66 74 80 Finished!
Maple
<lang Maple>flip := proc(arr, i) local start, temp, icopy; temp, start, icopy := 0,1,i: while (start < icopy) do arr[start], arr[icopy] := arr[icopy], arr[start]: start:=start+1: icopy:=icopy-1: end do: end proc: findMax := proc(arr, i) local Max, j: Max := 1: for j from 1 to i do if arr[j] > arr[Max] then Max := j: end if: end do: return Max: end proc: pancakesort := proc(arr) local len,i,Max; len := numelems(arr): for i from len to 2 by -1 do print(arr): Max := findMax(arr, i): if (not Max = i) then flip(arr, Max): flip(arr, i): end if: end do: print(arr); end proc:</lang>
- Example:
Input: arr := Array([17,3,72,0,36,2,3,8,40,1]):
[17, 3, 72, 0, 36, 2, 3, 8, 40, 1]
[1, 40, 8, 3, 2, 36, 0, 17, 3, 72]
[3, 17, 0, 36, 2, 3, 8, 1, 40, 72]
[1, 8, 3, 2, 3, 17, 0, 36, 40, 72]
[0, 1, 8, 3, 2, 3, 17, 36, 40, 72]
[3, 2, 3, 0, 1, 8, 17, 36, 40, 72]
[1, 0, 3, 2, 3, 8, 17, 36, 40, 72]
[2, 1, 0, 3, 3, 8, 17, 36, 40, 72]
[0, 1, 2, 3, 3, 8, 17, 36, 40, 72]
[0, 1, 2, 3, 3, 8, 17, 36, 40, 72]
Mathematica/Wolfram Language
<lang Mathematica>ClearAll[LMaxPosition, Flip, pancakeSort] LMaxPosition[a_, n_] :=
With[{b = Take[a, n]}, First[Ordering[b, -1]]]
SetAttributes[Flip, HoldAll]; Flip[a_] := Set[a, Reverse[a]] pancakeSort[in_] := Module[{n, lm, a = in},
For[n = Length[a], n > 1, n--, lm = LMaxPosition[a, n]; If[lm < n, Flip[a;; lm]; Print[a]; Flip[a;; n]; Print[a]; ]; ] ]
pancakeSort[{6, 7, 8, 9, 2, 5, 3, 4, 1}]</lang>
- Output:
{9,8,7,6,2,5,3,4,1}
{1,4,3,5,2,6,7,8,9}
{5,3,4,1,2,6,7,8,9}
{2,1,4,3,5,6,7,8,9}
{4,1,2,3,5,6,7,8,9}
{3,2,1,4,5,6,7,8,9}
{3,2,1,4,5,6,7,8,9}
{1,2,3,4,5,6,7,8,9}
MATLAB / Octave
<lang MATLAB>function list = pancakeSort(list)
for i = (numel(list):-1:2)
minElem = list(i);
minIndex = i;
%Find the min element in the current subset of the list
for j = (i:-1:1)
if list(j) <= minElem
minElem = list(j);
minIndex = j;
end
end
%If the element is already in the correct position don't flip
if i ~= minIndex
%First flip flips the min element in the stack to the top
list(minIndex:-1:1) = list(1:minIndex);
%Second flip flips the min element into the correct position in
%the stack
list(i:-1:1) = list(1:i);
end
end %for
end %pancakeSort</lang>
Sample Usage: <lang MATLAB>>> pancakeSort([4 3 1 5 6 2])
ans =
6 5 4 3 2 1</lang>
MAXScript
<lang MAXScript>fn flipArr arr index = ( local new = #() for i = index to 1 by -1 do ( append new arr[i] ) join new (for i in (index+1) to arr.count collect arr[i]) return new )
fn pancakeSort arr = ( if arr.count < 2 then return arr else ( for i = arr.count to 1 by -1 do ( local newArr = for n in 1 to i collect arr[n] local oldArr = for o in (i+1) to arr.count collect arr[o] local maxIndices = for m in 1 to (newArr.count) where (newArr[m] == amax newArr) collect m local lastMaxIndex = maxIndices[maxIndices.count] newArr = flipArr newArr lastMaxIndex newArr = flipArr newArr newArr.count arr = join newArr oldArr ) return arr ) )</lang> Output: <lang MAXScript> a = for i in 1 to 15 collect random 0 20
- (8, 13, 2, 0, 10, 8, 1, 15, 4, 7, 6, 9, 11, 3, 5)
pancakeSort a
- (0, 1, 2, 3, 4, 5, 6, 7, 8, 8, 9, 10, 11, 13, 15)
</lang>
NetRexx
Sorts integers, decimal numbers and strings because they're all the same to NetRexx. <lang NetRexx>/* NetRexx */ options replace format comments java crossref symbols nobinary
import java.util.List
runSample(arg) return
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method pancakeSort(tlist = List, debug = (1 == 0)) private static returns List
if tlist.size() > 1 then do
loop i_ = tlist.size() by -1 while i_ > 1
maxPos = 0
loop a_ = 0 while a_ < i_
if Rexx tlist.get(a_) > Rexx tlist.get(maxPos) then maxPos = a_
end a_
if maxPos = i_ - 1 then iterate i_
if maxPos > 0 then pancakeFlip(tlist, maxPos + 1, debug)
pancakeFlip(tlist, i_, debug)
end i_
end
return tlist
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method pancakeFlip(tlist = List, offset, debug = (1 == 0)) private static returns List
z_ = offset - 1
pl = 3
if debug then do
plx = offset.length()
if plx > pl then pl = plx
say ' flip{1-'offset.right(pl, 0)'} Before:' tlist
end
loop i_ = 0 while i_ < z_
Collections.swap(tlist, i_, z_)
z_ = z_ - 1
end i_
if debug then do
say ' flip{1-'offset.right(pl, 0)'} After:' tlist
end
return tlist
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method runSample(arg) private static
isTrue = (1 == 1) isFalse = \isTrue parse arg debug . if '-debug'.abbrev(debug.lower(), 2) then debug = isTrue else debug = isFalse
lists = sampleData() loop il = 1 to lists[0] clist = words2list(lists[il]) say ' Input:' clist say 'Output:' pancakeSort(clist, debug) say end il
return
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method sampleData() private static
lists = i_ = 0 i_ = i_ + 1; lists[0] = i_; lists[i_] = '1 4 3 5 2 9 8 7 6' i_ = i_ + 1; lists[0] = i_; lists[i_] = '10 -9 8 -7 6 -5 4 -3 2 -1 0 -10 9 -8 7 -6 5 -4 3 -2 1' i_ = i_ + 1; lists[0] = i_; lists[i_] = '88 18 31 44 4 0 8 81 14 78 20 76 84 33 73 75 82 5 62 70 12 7 1' i_ = i_ + 1; lists[0] = i_; lists[i_] = '10 10.0 10.00 1 -10.0 10. -1' i_ = i_ + 1; lists[0] = i_; lists[i_] = 'To be or not to be that is the question' i_ = i_ + 1; lists[0] = i_; lists[i_] = '1' return lists
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method words2list(wordlist) private static returns List
clist = ArrayList() loop w_ = 1 to wordlist.words() clist.add(wordlist.word(w_)) end w_
return clist
</lang>
- Output:
Input: [1, 4, 3, 5, 2, 9, 8, 7, 6] Output: [1, 2, 3, 4, 5, 6, 7, 8, 9] Input: [10, -9, 8, -7, 6, -5, 4, -3, 2, -1, 0, -10, 9, -8, 7, -6, 5, -4, 3, -2, 1] Output: [-10, -9, -8, -7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10] Input: [88, 18, 31, 44, 4, 0, 8, 81, 14, 78, 20, 76, 84, 33, 73, 75, 82, 5, 62, 70, 12, 7, 1] Output: [0, 1, 4, 5, 7, 8, 12, 14, 18, 20, 31, 33, 44, 62, 70, 73, 75, 76, 78, 81, 82, 84, 88] Input: [10, 10.0, 10.00, 1, -10.0, 10., -1] Output: [-10.0, -1, 1, 10.00, 10.0, 10., 10] Input: [To, be, or, not, to, be, that, is, the, question] Output: [be, be, is, not, or, question, that, the, to, To] Input: [1] Output: [1]
Nim
<lang nim>import algorithm
proc pancakeSort[T](list: var openarray[T]) =
var length = list.len if length < 2: return
var moves = 0
for i in countdown(length, 2):
var maxNumPos = 0
for a in 0 ..< i:
if list[a] > list[maxNumPos]:
maxNumPos = a
if maxNumPos == i - 1: continue
if maxNumPos > 0:
inc moves
reverse(list, 0, maxNumPos)
inc moves reverse(list, 0, i - 1)
var a = @[4, 65, 2, -31, 0, 99, 2, 83, 782] pancakeSort a echo a</lang> Output:
@[-31, 0, 2, 2, 4, 65, 83, 99, 782]
OCaml
<lang ocaml>let rec sorted = function
| [] -> (true) | x::y::_ when x > y -> (false) | x::xs -> sorted xs
let rev_until_max li =
let rec aux acc greater prefix suffix = function | x::xs when x > greater -> aux (x::acc) x acc xs xs | x::xs -> aux (x::acc) greater prefix suffix xs | [] -> (greater, (prefix @ suffix)) in aux [] min_int [] li li
let pancake_sort li =
let rec aux i li suffix = let greater, li = rev_until_max li in let suffix = greater :: suffix and li = List.rev li in if sorted li then (li @ suffix), i else aux (succ i) li suffix in aux 0 li []
let print_list li =
List.iter (Printf.printf " %d") li; print_newline()
let make_rand_list n bound =
let rec aux acc i = if i >= n then (acc) else aux ((Random.int bound)::acc) (succ i) in aux [] 0
let () =
Random.self_init(); let li = make_rand_list 8 100 in print_list li; let res, n = pancake_sort li in print_list res; Printf.printf " sorted in %d loops\n" n;
- </lang>
PARI/GP
<lang parigp>pancakeSort(v)={
my(top=#v);
while(top>1,
my(mx=1,t);
for(i=2,top,if(v[i]>v[mx], mx=i));
if(mx==top, top--; next);
for(i=1,mx\2,
t=v[i];
v[i]=v[mx+1-i];
v[mx+1-i]=t
);
for(i=1,top\2,
t=v[i];
v[i]=v[top+1-i];
v[top+1-i]=t
);
top--
);
v
};</lang>
Pascal
<lang pascal>Program PancakeSort (output);
procedure flip(var b: array of integer; last: integer);
var swap, i: integer;
begin
for i := low(b) to (last - low(b) - 1) div 2 do
begin
swap := b[i];
b[i] := b[last-(i-low(b))];
b[last-(i-low(b))] := swap;
end;
end;
procedure PancakeSort(var a: array of integer);
var i, j, maxpos: integer;
begin for i := high(a) downto low(a) do begin
// Find position of max number between beginning and i
maxpos := i;
for j := low(a) to i - 1 do
if a[j] > a[maxpos] then
maxpos := j;
// is it in the correct position already?
if maxpos = i then
continue;
// is it at the beginning of the array? If not flip array section so it is
if maxpos <> low(a) then
flip(a, maxpos);
// Flip array section to get max number to correct position
flip(a, i); end; end;
var
data: array of integer; i: integer;
begin
setlength(data, 8);
Randomize;
writeln('The data before sorting:');
for i := low(data) to high(data) do
begin
data[i] := Random(high(data));
write(data[i]:4);
end;
writeln;
PancakeSort(data);
writeln('The data after sorting:');
for i := low(data) to high(data) do
begin
write(data[i]:4);
end;
writeln;
end.</lang> Output:
:>./PancakeSort The data before sorting: 3 1 3 2 4 0 2 6 The data after sorting: 0 1 2 2 3 3 4 6
Perl
<lang perl>sub pancake {
my @x = @_;
for my $idx (0 .. $#x - 1) {
my $min = $idx;
$x[$min] > $x[$_] and $min = $_ for $idx + 1 .. $#x;
next if $x[$min] == $x[$idx];
@x[$min .. $#x] = reverse @x[$min .. $#x] if $x[$min] != $x[-1];
@x[$idx .. $#x] = reverse @x[$idx .. $#x];
}
@x;
}
my @a = map (int rand(100), 1 .. 10); print "Before @a\n"; @a = pancake(@a); print "After @a\n"; </lang> Sample output:
Before 57 37 35 35 22 58 70 53 77 15 After 15 22 35 35 37 53 57 58 70 77
Phix
with javascript_semantics function pancake_sort(sequence s) s = deep_copy(s) for i=length(s) to 2 by -1 do integer m = largest(s[1..i],true) if m<i then if m>1 then s[1..m] = reverse(s[1..m]) end if s[1..i] = reverse(s[1..i]) end if end for return s end function constant s = shuffle(tagset(10)) ? s ? pancake_sort(s)
- Output:
{2,8,6,1,5,10,3,4,9,7}
{1,2,3,4,5,6,7,8,9,10}
PicoLisp
<lang PicoLisp>(de pancake (Lst)
(prog1 (flip Lst (index (apply max Lst) Lst))
(for (L @ (cdr (setq Lst (cdr L))) (cdr L))
(con L (flip Lst (index (apply max Lst) Lst))) ) ) )</lang>
Output:
: (trace 'flip) -> flip : (pancake (6 7 2 1 8 9 5 3 4)) flip : (6 7 2 1 8 9 5 3 4) 6 flip = (9 8 1 2 7 6 5 3 4) flip : (8 1 2 7 6 5 3 4) 1 flip = (8 1 2 7 6 5 3 4) flip : (1 2 7 6 5 3 4) 3 flip = (7 2 1 6 5 3 4) flip : (2 1 6 5 3 4) 3 flip = (6 1 2 5 3 4) flip : (1 2 5 3 4) 3 flip = (5 2 1 3 4) flip : (2 1 3 4) 4 flip = (4 3 1 2) flip : (3 1 2) 1 flip = (3 1 2) flip : (1 2) 2 flip = (2 1) -> (9 8 7 6 5 4 3 2 1)
PL/I
<lang PL/I> pancake_sort: procedure options (main); /* 23 April 2009 */
declare a(10) fixed, (i, n, loc) fixed binary;
a(1) = 3; a(2) = 9; a(3) = 2; a(4) = 7; a(5) = 10; a(6) = 1; a(7) = 8; a(8) = 5; a(9) = 4; a(10) = 6;
n = hbound(A,1);
put skip edit (A) (f(5));
do i = 1 to n-1;
loc = max(A, n);
call flip (A, loc);
call flip (A, n);
n = n - 1;
put skip edit (A) (f(5));
end;
max: procedure (A, k) returns (fixed binary);
declare A(*) fixed, k fixed binary;
declare (i, maximum, loc) fixed binary;
maximum = A(1); loc = 1;
do i = 2 to k;
if A(i) > maximum then do; maximum = A(i); loc = i; end;
end;
return (loc);
end max;
flip: procedure (A, k);
declare A(*) fixed, k fixed binary;
declare (i, t) fixed binary;
do i = 1 to (k+1)/2;
t = A(i); A(i) = A(k-i+1); A(k-i+1) = t;
end;
end flip;
end pancake_sort; </lang> Output: <lang>
3 9 2 7 10 1 8 5 4 6 6 4 5 8 1 3 9 2 7 10 7 2 6 4 5 8 1 3 9 10 3 1 7 2 6 4 5 8 9 10 5 4 6 2 3 1 7 8 9 10 1 3 2 5 4 6 7 8 9 10 4 1 3 2 5 6 7 8 9 10 2 3 1 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
</lang>
PowerShell
<lang PowerShell>Function FlipPancake( [Object[]] $indata, $index = 1 ) { $data=$indata.Clone() $datal = $data.length - 1 if( $index -gt 0 ) { if( $datal -gt $index ) { $first = $data[ $index..0 ] $last = $data[ ( $index + 1 )..$datal ] $data = $first + $last } else { $data = $data[ $index..0 ] } } $data }
Function MaxIdx( [Object[]] $data ) { $data | ForEach-Object { $max = $data[ 0 ]; $i = 0; $maxi = 0 } { if( $_ -gt $max ) { $max = $_; $maxi = $i }; $i++ } { $maxi } }
Function PancakeSort( [Object[]] $data, $index = 0 ) { "unsorted - $data" $datal = $data.length - 1 if( $datal -gt 0 ) { for( $i = $datal; $i -gt 0; $i-- ) { $data = FlipPancake ( FlipPancake $data ( MaxIdx $data[ 0..$i ] ) ) $i } } "sorted - $data" }
$l = 100; PancakeSort ( 1..$l | ForEach-Object { $Rand = New-Object Random }{ $Rand.Next( 0, $l - 1 ) } )</lang>
PureBasic
<lang PureBasic>If OpenConsole()
Define i, j, k, Loops
Dim Pile(9)
;--------------------------------------------------------------
;- Create a Random Pile()
For i=1 To 9 ;- Initiate the Pile
Pile(i)=i
Next
For i=9 To 1 Step -1 ;- Do a Fisher-Yates shuffle
Swap Pile(i),Pile(Random(i-1)+1)
Next
Print("Random Pile() :")
For i=1 To 9
Print(" "+Str(Pile(i)))
Next
;--------------------------------------------------------------
;- Start Sorting
For i=9 To 2 Step -1
If Pile(i)<>i ;- Only Flip it if the current cake need Swapping
Loops+1
j=0
Repeat ;- find place of Pancake(i) in the Pile()
j+1
Until Pile(j)=i
For k=1 To (j/2) ;- Flip it up
Swap Pile(k),Pile(j-k+1)
Next
For k=1 To i/2 ;- Flip in place
Swap Pile(k),Pile(i-k+1)
Next
EndIf
Next
Print(#CRLF$+"Resulting Pile() :")
For i=1 To 9
Print(" "+str(Pile(i)))
Next
Print(#CRLF$+"All done in "+str(Loops)+" loops.")
Print(#CRLF$+#CRLF$+"Press ENTER to quit."): Input()
CloseConsole()
EndIf</lang>
Output can look like
Original Pile() : 9 4 1 8 6 3 2 5 7 Resulting Pile() : 1 2 3 4 5 6 7 8 9 All done in 6 loops. Press ENTER to quit.
Python
The function: <lang python>tutor = False
def pancakesort(data):
if len(data) <= 1:
return data
if tutor: print()
for size in range(len(data), 1, -1):
maxindex = max(range(size), key=data.__getitem__)
if maxindex+1 != size:
# This indexed max needs moving
if maxindex != 0:
# Flip the max item to the left
if tutor: print('With: %r doflip %i'
% ( ' '.join(str(x) for x in data), maxindex+1 ))
data[:maxindex+1] = reversed(data[:maxindex+1])
# Flip it into its final position
if tutor: print('With: %r doflip %i'
% ( ' '.join(str(x) for x in data), size ))
data[:size] = reversed(data[:size])
if tutor: print()</lang>
A test: <lang python>if __name__ == '__main__':
import random
tutor = True
data = list('123456789')
while data == sorted(data):
random.shuffle(data)
print('Original List: %r' % ' '.join(data))
pancakesort(data)
print('Pancake Sorted List: %r' % ' '.join(data))</lang>
Sample output:
Original List: '6 7 2 1 8 9 5 3 4' With: '6 7 2 1 8 9 5 3 4' doflip 6 With: '9 8 1 2 7 6 5 3 4' doflip 9 With: '4 3 5 6 7 2 1 8 9' doflip 5 With: '7 6 5 3 4 2 1 8 9' doflip 7 With: '1 2 4 3 5 6 7 8 9' doflip 3 With: '4 2 1 3 5 6 7 8 9' doflip 4 With: '3 1 2 4 5 6 7 8 9' doflip 3 With: '2 1 3 4 5 6 7 8 9' doflip 2 Pancake Sorted List: '1 2 3 4 5 6 7 8 9'
Quackery
<lang Quackery>[ split reverse join ] is flip ( [ n --> [ )
[ 0 swap behead swap
witheach
[ 2dup > iff
[ nip nip
i^ 1+ swap ]
else drop ]
drop ] is smallest ( [ --> n )
[ dup size times
[ dup i^ split nip
smallest i^ + flip
i^ flip ] ] is pancakesort ( [ --> [ )</lang>
Testing in Quackery shell:
/O> [] 23 times [ 10 random join ] ... say "Before: " dup echo cr ... say " After: " pancakesort echo cr ... Before: [ 1 2 1 5 5 9 7 1 2 3 9 1 9 2 5 0 5 2 6 0 8 3 2 ] After: [ 0 0 1 1 1 1 2 2 2 2 2 3 3 5 5 5 5 6 7 8 9 9 9 ] Stack empty.
Racket
<lang racket>
- lang racket
(define (pancake-sort l)
(define (flip l n) (append (reverse (take l n)) (drop l n)))
(for/fold ([l l]) ([i (in-range (length l) 1 -1)])
(let* ([i2 (cdr (for/fold ([m #f]) ([x l] [j i])
(if (and m (<= x (car m))) m (cons x j))))]
[l (if (zero? i2) l (flip l (add1 i2)))])
(flip l i))))
(pancake-sort (shuffle (range 0 10)))
- => '(0 1 2 3 4 5 6 7 8 9)
</lang>
Raku
(formerly Perl 6) <lang perl6>sub pancake_sort ( @a is copy ) {
my $endpoint = @a.end;
while $endpoint > 0 and not [<] @a {
my $max_i = [0..$endpoint].max: { @a[$_] };
my $max = @a[$max_i];
if @a[$endpoint] == $max {
$endpoint-- while @a[$endpoint] == $max;
next;
}
# @a[$endpoint] is not $max, so it needs flipping;
# Flip twice if max is not already at the top.
@a[0..$max_i] .= reverse if $max_i != 0;
@a[0..$endpoint] .= reverse;
$endpoint--;
}
return @a;
} my @data = 6, 7, 2, 1, 8, 9, 5, 3, 4; say 'input = ' ~ @data; say 'output = ' ~ @data.&pancake_sort; </lang>
Output:
input = 6 7 2 1 8 9 5 3 4 output = 1 2 3 4 5 6 7 8 9
REXX
<lang rexx>/*REXX program sorts and displays an array using the pancake sort algorithm. */ call gen /*generate elements in the @. array.*/ call show 'before sort' /*display the BEFORE array elements.*/ say copies('▒', 60) /*display a separator line for eyeballs*/ call pancakeSort # /*invoke the pancake sort. Yummy. */ call show ' after sort' /*display the AFTER array elements. */ exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ flip: parse arg y; do i=1 for (y+1)%2; yyy=y-i+1; _=@.i; @.i=@.yyy; @.yyy=_; end; return show: do k=1 for #; say @element right(k,length(#)) arg(1)':' right(@.k,9); end; return /*──────────────────────────────────────────────────────────────────────────────────────*/ gen: fibs= '-55 -21 -1 -8 -8 -21 -55 0 0' /*some non─positive Fibonacci numbers, */
@element= right('element', 21) /* most Fibs of which are repeated.*/
/* ┌◄─┬──◄─ some paired bread primes which are of the form: (P-3)÷2 and 2∙P+3 */
/* │ │ where P is a prime. Bread primes are related to sandwich & meat primes*/
/* ↓ ↓ ──── ════ ───── ══════ ────── ══════ ────── ═══════ ─────── ═══════ ──────*/
bp=2 17 5 29 7 37 13 61 43 181 47 197 67 277 97 397 113 461 137 557 167 677 173 701,
797 1117 307 1237 1597 463 1861 467
$=bp fibs; #=words($) /*combine the two lists; get # of items*/
do j=1 for #; @.j=word($,j); end /*◄─── obtain a number from the $ list.*/
return /* [↑] populate the @. array with #s*/
/*──────────────────────────────────────────────────────────────────────────────────────*/ pancakeSort: procedure expose @.; parse arg N
do N=N by -1 for N-1
!= @.1; ?= 1; do j=2 to N; if @.j<=! then iterate
!= @.j; ?= j
end /*j*/
call flip ?; call flip N
end /*N*/
return</lang>
- output when using the internally generated numbers:
(Shown at three-quarter size.)
element 1 before sort: 2
element 2 before sort: 17
element 3 before sort: 5
element 4 before sort: 29
element 5 before sort: 7
element 6 before sort: 37
element 7 before sort: 13
element 8 before sort: 61
element 9 before sort: 43
element 10 before sort: 181
element 11 before sort: 47
element 12 before sort: 197
element 13 before sort: 67
element 14 before sort: 277
element 15 before sort: 97
element 16 before sort: 397
element 17 before sort: 113
element 18 before sort: 461
element 19 before sort: 137
element 20 before sort: 557
element 21 before sort: 167
element 22 before sort: 677
element 23 before sort: 173
element 24 before sort: 701
element 25 before sort: 797
element 26 before sort: 1117
element 27 before sort: 307
element 28 before sort: 1237
element 29 before sort: 1597
element 30 before sort: 463
element 31 before sort: 1861
element 32 before sort: 467
element 33 before sort: -55
element 34 before sort: -21
element 35 before sort: -1
element 36 before sort: -8
element 37 before sort: -8
element 38 before sort: -21
element 39 before sort: -55
element 40 before sort: 0
element 41 before sort: 0
▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒
element 1 after sort: -55
element 2 after sort: -55
element 3 after sort: -21
element 4 after sort: -21
element 5 after sort: -8
element 6 after sort: -8
element 7 after sort: -1
element 8 after sort: 0
element 9 after sort: 0
element 10 after sort: 2
element 11 after sort: 5
element 12 after sort: 7
element 13 after sort: 13
element 14 after sort: 17
element 15 after sort: 29
element 16 after sort: 37
element 17 after sort: 43
element 18 after sort: 47
element 19 after sort: 61
element 20 after sort: 67
element 21 after sort: 97
element 22 after sort: 113
element 23 after sort: 137
element 24 after sort: 167
element 25 after sort: 173
element 26 after sort: 181
element 27 after sort: 197
element 28 after sort: 277
element 29 after sort: 307
element 30 after sort: 397
element 31 after sort: 461
element 32 after sort: 463
element 33 after sort: 467
element 34 after sort: 557
element 35 after sort: 677
element 36 after sort: 701
element 37 after sort: 797
element 38 after sort: 1117
element 39 after sort: 1237
element 40 after sort: 1597
element 41 after sort: 1861
Ring
<lang ring> pancakeList = [6, 7, 8, 9, 2, 5, 3, 4, 1] flag = 0 see "Before :" + nl for n = 1 to len(pancakeList)
see pancakeList[n] + " "
next see nl
pancakeSort(pancakeList)
see "After :" + nl for n = 1 to len(pancakeList)
see pancakeList[n] + " "
next see nl
func pancakeSort A
n = len(A)
while flag = 0
flag = 1
for i = 1 to n-1
if A[i] < A[i+1]
temp = A[i]
A[i] = A[i+1]
A [i+1] = temp
flag = 0 ok
next
end
return A
</lang> Output:
Before : 678925341 After : 987654321
Ruby
<lang ruby>class Array
def pancake_sort!
num_flips = 0
(self.size-1).downto(1) do |end_idx|
max = self[0..end_idx].max
max_idx = self[0..end_idx].index(max)
next if max_idx == end_idx
if max_idx > 0
self[0..max_idx] = self[0..max_idx].reverse
p [num_flips += 1, self] if $DEBUG
end
self[0..end_idx] = self[0..end_idx].reverse
p [num_flips += 1, self] if $DEBUG
end
self
end
end
p a = (1..9).to_a.shuffle p a.pancake_sort!</lang>
sample output:
$ ruby -d sorting_pancake.rb [7, 3, 6, 8, 2, 4, 5, 1, 9] [1, [8, 6, 3, 7, 2, 4, 5, 1, 9]] [2, [1, 5, 4, 2, 7, 3, 6, 8, 9]] [3, [7, 2, 4, 5, 1, 3, 6, 8, 9]] [4, [6, 3, 1, 5, 4, 2, 7, 8, 9]] [5, [2, 4, 5, 1, 3, 6, 7, 8, 9]] [6, [5, 4, 2, 1, 3, 6, 7, 8, 9]] [7, [3, 1, 2, 4, 5, 6, 7, 8, 9]] [8, [2, 1, 3, 4, 5, 6, 7, 8, 9]] [9, [1, 2, 3, 4, 5, 6, 7, 8, 9]] [1, 2, 3, 4, 5, 6, 7, 8, 9]
Rust
<lang Rust>fn pancake_sort<T: Ord>(v: &mut [T]) {
let len = v.len();
// trivial case -- no flips
if len < 2 {
return;
}
for i in (0..len).rev() {
// find index of the maximum element within `v[0..i]` (inclusive)
let max_index = v.iter()
.take(i + 1)
.enumerate()
.max_by_key(|&(_, elem)| elem)
.map(|(idx, _)| idx)
// safe because we already checked if `v` is empty
.unwrap();
// if `max_index` is not where it's supposed to be
// do two flips to move it to `i`
if max_index != i {
flip(v, max_index);
flip(v, i);
}
}
}
// function to flip a section of a mutable collection from 0..num (inclusive) fn flip<E: PartialOrd>(v: &mut [E], num: usize) {
v[0..num + 1].reverse();
}
fn main() {
// Sort numbers
let mut numbers = [4, 65, 2, -31, 0, 99, 2, 83, 782, 1];
println!("Before: {:?}", numbers);
pancake_sort(&mut numbers);
println!("After: {:?}", numbers);
// Sort strings
let mut strings = ["beach", "hotel", "airplane", "car", "house", "art"];
println!("Before: {:?}", strings);
pancake_sort(&mut strings);
println!("After: {:?}", strings);
}</lang>
Sidef
<lang ruby>func pancake(a) {
for idx in ^(a.end) {
var min = idx
for i in (idx+1 .. a.end) { min = i if (a[min] > a[i]) }
next if (a[min] == a[idx])
a[min..a.end] = [a[min..a.end]].reverse...
a[idx..a.end] = [a[idx..a.end]].reverse...
}
return a
}
var arr = 10.of{ 100.irand } say "Before: #{arr}" say "After: #{pancake(arr)}"</lang>
- Output:
Before: 61 29 68 15 34 2 32 54 73 43 After: 2 15 29 32 34 43 54 61 68 73
Swift
<lang Swift>import Foundation
struct PancakeSort {
var arr:[Int]
mutating func flip(n:Int) {
for i in 0 ..< (n + 1) / 2 {
swap(&arr[n - i], &arr[i])
}
println("flip(0.. \(n)): \(arr)")
}
func minmax(n:Int) -> [Int] {
var xm = arr[0]
var xM = arr[0]
var posm = 0
var posM = 0
for i in 1..<n {
if (arr[i] < xm) {
xm = arr[i]
posm = i
} else if (arr[i] > xM) {
xM = arr[i]
posM = i
}
}
return [posm, posM]
}
mutating func sort(var n:Int, var dir:Int) {
if n == 0 {
return
}
let mM = minmax(n)
let bestXPos = mM[dir]
let altXPos = mM[1 - dir]
var flipped = false
if bestXPos == n - 1 {
n--
} else if bestXPos == 0 {
flip(n - 1)
n--
} else if altXPos == n - 1 {
dir = 1 - dir
n--
flipped = true
} else {
flip(bestXPos)
}
sort(n, dir: dir)
if flipped {
flip(n)
}
}
}
let arr = [2, 3, 6, 1, 4, 5, 10, 8, 7, 9] var a = PancakeSort(arr: arr) a.sort(arr.count, dir: 1) println(a.arr)</lang>
- Output:
flip(0.. 6): [10, 5, 4, 1, 6, 3, 2, 8, 7, 9] flip(0.. 9): [9, 7, 8, 2, 3, 6, 1, 4, 5, 10] flip(0.. 8): [5, 4, 1, 6, 3, 2, 8, 7, 9, 10] flip(0.. 6): [8, 2, 3, 6, 1, 4, 5, 7, 9, 10] flip(0.. 7): [7, 5, 4, 1, 6, 3, 2, 8, 9, 10] flip(0.. 6): [2, 3, 6, 1, 4, 5, 7, 8, 9, 10] flip(0.. 2): [6, 3, 2, 1, 4, 5, 7, 8, 9, 10] flip(0.. 5): [5, 4, 1, 2, 3, 6, 7, 8, 9, 10] flip(0.. 4): [3, 2, 1, 4, 5, 6, 7, 8, 9, 10] flip(0.. 2): [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Tailspin
Simplest version, bubblesort style <lang tailspin> templates pancakeSort
@: {stack: $, flips: 0};
sink flip
when <2..> do
@pancakeSort.stack(1..$): $@pancakeSort.stack($..1:-1)...;
'$@pancakeSort.stack;$#10;' -> !OUT::write
@pancakeSort.flips: $@pancakeSort.flips + 1;
end flip
sink fixTop
@: 1;
2..$ -> #
$ -> \(when <~=$@fixTop> do $@fixTop -> !flip $ -> !flip \) -> !VOID
when <?($@pancakeSort.stack($) <$@pancakeSort.stack($@)..>)> do @: $;
end fixTop
$::length..2:-1 -> !fixTop
$@ !
end pancakeSort
[6,7,2,1,8,9,5,3,4] -> pancakeSort -> !OUT::write </lang>
- Output:
[9, 8, 1, 2, 7, 6, 5, 3, 4]
[4, 3, 5, 6, 7, 2, 1, 8, 9]
[7, 6, 5, 3, 4, 2, 1, 8, 9]
[1, 2, 4, 3, 5, 6, 7, 8, 9]
[4, 2, 1, 3, 5, 6, 7, 8, 9]
[3, 1, 2, 4, 5, 6, 7, 8, 9]
[2, 1, 3, 4, 5, 6, 7, 8, 9]
[1, 2, 3, 4, 5, 6, 7, 8, 9]
{flips=8, stack=[1, 2, 3, 4, 5, 6, 7, 8, 9]}
Tcl
<lang tcl>package require Tcl 8.5
- Some simple helper procedures
proc flip {nlist n} {
concat [lreverse [lrange $nlist 0 $n]] [lrange $nlist $n+1 end]
} proc findmax {nlist limit} {
lsearch -exact $nlist [tcl::mathfunc::max {*}[lrange $nlist 0 $limit]]
}
- Simple-minded pancake sort algorithm
proc pancakeSort {nlist {debug ""}} {
for {set i [llength $nlist]} {[incr i -1] > 0} {} {
set j [findmax $nlist $i] if {$i != $j} { if {$j} { set nlist [flip $nlist $j] if {$debug eq "debug"} {puts [incr flips]>>$nlist} } set nlist [flip $nlist $i] if {$debug eq "debug"} {puts [incr flips]>>$nlist} }
} return $nlist
}</lang> Demonstrate (with debug mode enabled so it prints intermediate states): <lang tcl>puts [pancakeSort {27916 5928 23535 14711 32184 14621 21093 14422 29844 11093} debug]</lang> Output:
1>>32184 14711 23535 5928 27916 14621 21093 14422 29844 11093 2>>11093 29844 14422 21093 14621 27916 5928 23535 14711 32184 3>>29844 11093 14422 21093 14621 27916 5928 23535 14711 32184 4>>14711 23535 5928 27916 14621 21093 14422 11093 29844 32184 5>>27916 5928 23535 14711 14621 21093 14422 11093 29844 32184 6>>11093 14422 21093 14621 14711 23535 5928 27916 29844 32184 7>>23535 14711 14621 21093 14422 11093 5928 27916 29844 32184 8>>5928 11093 14422 21093 14621 14711 23535 27916 29844 32184 9>>21093 14422 11093 5928 14621 14711 23535 27916 29844 32184 10>>14711 14621 5928 11093 14422 21093 23535 27916 29844 32184 11>>14422 11093 5928 14621 14711 21093 23535 27916 29844 32184 12>>5928 11093 14422 14621 14711 21093 23535 27916 29844 32184 5928 11093 14422 14621 14711 21093 23535 27916 29844 32184
As you can see, it took 12 flips.
Transd
<lang scheme>
- lang transd
MainModule: {
vint: [ 9, 0, 5, 10, 3, -3, -1, 8, -7, -4, -2, -6, 2, 4, 6, -10, 7, -8, -5, 1, -9],
_start: (λ (with n (- (size vint) 1) m 0
(textout vint "\n")
(while n
(= m (max-element-idx vint Range(0 (+ n 1))))
(if (neq m n)
(if m (reverse vint Range(0 (+ m 1))))
(reverse vint Range(0 (+ n 1))))
(-= n 1)
)
(textout vint "\n")
))
}</lang>
- Output:
[9, 0, 5, 10, 3, -3, -1, 8, -7, -4, -2, -6, 2, 4, 6, -10, 7, -8, -5, 1, -9] [-10, -9, -8, -7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
uBasic/4tH
<lang>PRINT "Pancake sort:"
n = FUNC (_InitArray) PROC _ShowArray (n) PROC _Pancakesort (n) PROC _ShowArray (n)
END
_Flip PARAM(1)
LOCAL(1)
b@ = 0
DO WHILE b@ < a@ PROC _Swap (b@, a@) b@ = b@ + 1 a@ = a@ - 1 LOOP
RETURN
_Pancakesort PARAM (1) ' Pancakesort
LOCAL(3)
IF a@ < 2 THEN RETURN
FOR b@ = a@ TO 2 STEP -1
c@ = 0
FOR d@ = 0 TO b@ - 1
IF @(d@) > @(c@) THEN c@ = d@
NEXT
IF c@ = b@ - 1 THEN CONTINUE IF c@ THEN PROC _Flip (c@) PROC _Flip (b@ - 1)
NEXT
RETURN
_Swap PARAM(2) ' Swap two array elements
PUSH @(a@) @(a@) = @(b@) @(b@) = POP()
RETURN
_InitArray ' Init example array
PUSH 4, 65, 2, -31, 0, 99, 2, 83, 782, 1 FOR i = 0 TO 9 @(i) = POP() NEXT
RETURN (i)
_ShowArray PARAM (1) ' Show array subroutine
FOR i = 0 TO a@-1 PRINT @(i), NEXT PRINT
RETURN</lang>
UNIX Shell
This takes advantage of the semi-standard UNIX utility shuf to randomize the initial array.
<lang sh>#!/usr/bin/env bash main() {
local stack
local -i n m i
if (( $# )); then
stack=("$@")
else
stack=($(printf '%s\n' {0..9} | shuf))
fi
print_stack 0 "${stack[@]}"
# start by looking at whole stack
(( n = ${#stack[@]} ))
# keep going until we're all sorted while (( n > 0 )); do
# shrink the stack until its bottom is not the right size
while (( n > 0 && ${stack[n-1]} == n-1 )); do
(( n-=1 ))
done
# if we got to the top we're done
if (( n == 0 )); then
break
fi
# find the index of the largest pancake in the unsorted stack
m=0
for (( i=1; i < n-1; ++i )); do
if (( ${stack[i]} > ${stack[m]} )); then
(( m = i ))
fi
done
# if it's not on top, flip to get it there
if (( m > 0 )); then
stack=( $(flip "$(( m + 1 ))" "${stack[@]}") )
print_stack "$(( m + 1))" "${stack[@]}"
fi
# now flip the top to the bottom
stack=( $(flip "$n" "${stack[@]}" ) )
print_stack "$n" "${stack[@]}"
# and move up
(( n -= 1 ))
done
print_stack 0 "${stack[@]}"
}
- display the stack, optionally with brackets around a prefix
print_stack() {
local prefix=$1
shift
if (( prefix )); then
printf '[%s' "$1"
if (( prefix > 1 )); then
printf ',%s' "${@:2:prefix-1}"
fi
printf ']'
else
printf ' '
fi
if (( prefix < $# )); then
printf '%s' "${@:prefix+1:1}"
if (( prefix+1 < $# )); then
printf ',%s' "${@:prefix+2:$#-prefix-1}"
fi
fi
printf '\n'
}
- reverse the first N elements of an array
flip() {
local -i size end midpoint i
local stack temp
size=$1
shift
stack=( "$@" )
if (( size > 1 )); then
(( end = size - 1 ))
(( midpoint = size/2 + size % 2 ))
for (( i=0; i<midpoint; ++i )); do
temp=${stack[i]}
stack[i]=${stack[size-1-i]}
stack[size-1-i]=$temp
done
fi
printf '%s\n' "${stack[@]}"
}
main "$@"</lang>
- Output:
Sample run:
3,0,9,7,6,1,2,5,4,8 [9,0,3]7,6,1,2,5,4,8 [8,4,5,2,1,6,7,3,0,9] [0,3,7,6,1,2,5,4,8]9 [7,3,0]6,1,2,5,4,8,9 [4,5,2,1,6,0,3,7]8,9 [6,1,2,5,4]0,3,7,8,9 [3,0,4,5,2,1,6]7,8,9 [5,4,0,3]2,1,6,7,8,9 [1,2,3,0,4,5]6,7,8,9 [3,2,1]0,4,5,6,7,8,9 [0,1,2,3]4,5,6,7,8,9 0,1,2,3,4,5,6,7,8,9
VBA
<lang vb>
'pancake sort 'uses two auxiliary routines "printarray" and "flip"
Public Sub printarray(A)
For i = LBound(A) To UBound(A) Debug.Print A(i), Next Debug.Print
End Sub
Public Sub Flip(ByRef A, p1, p2, trace) 'flip first elements of A (p1 to p2)
If trace Then Debug.Print "we'll flip the first "; p2 - p1 + 1; "elements of the array" Cut = Int((p2 - p1 + 1) / 2) For i = 0 To Cut - 1 'flip position i and (n - i + 1) temp = A(i) A(i) = A(p2 - i) A(p2 - i) = temp Next
End Sub
Public Sub pancakesort(ByRef A(), Optional trace As Boolean = False) 'sort A into ascending order using pancake sort
lb = LBound(A) ub = UBound(A) Length = ub - lb + 1 If Length <= 1 Then 'no need to sort
Exit Sub
End If
For i = ub To lb + 1 Step -1
'find position of max. element in subarray A(lowerbound to i)
P = lb
Maximum = A(P)
For j = lb + 1 To i
If A(j) > Maximum Then
P = j
Maximum = A(j)
End If
Next j
'check if maximum is already at end - then we don't need to flip
If P < i Then
'flip the first part of the array up to the maximum so it is at the head - skip if it is already there
If P > 1 Then
Flip A, lb, P, trace
If trace Then printarray A
End If
'now flip again so that it is in its final position
Flip A, lb, i, trace
If trace Then printarray A
End If
Next i End Sub
'test routine Public Sub TestPancake(Optional trace As Boolean = False) Dim A() A = Array(5, 7, 8, 3, 1, 10, 9, 23, 50, 0) Debug.Print "Initial array:" printarray A pancakesort A, trace Debug.Print "Final array:" printarray A End Sub </lang>
Sample output:
testpancake True Initial array: 5 7 8 3 1 10 9 23 50 0 we'll flip the first 9 elements of the array 50 23 9 10 1 3 8 7 5 0 we'll flip the first 10 elements of the array 0 5 7 8 3 1 10 9 23 50 we'll flip the first 7 elements of the array 10 1 3 8 7 5 0 9 23 50 we'll flip the first 8 elements of the array 9 0 5 7 8 3 1 10 23 50 we'll flip the first 7 elements of the array 1 3 8 7 5 0 9 10 23 50 we'll flip the first 3 elements of the array 8 3 1 7 5 0 9 10 23 50 we'll flip the first 6 elements of the array 0 5 7 1 3 8 9 10 23 50 we'll flip the first 3 elements of the array 7 5 0 1 3 8 9 10 23 50 we'll flip the first 5 elements of the array 3 1 0 5 7 8 9 10 23 50 we'll flip the first 3 elements of the array 0 1 3 5 7 8 9 10 23 50 Final array: 0 1 3 5 7 8 9 10 23 50
Wren
<lang ecmascript>import "/sort" for Find
class Pancake {
construct new(a) {
_a = a.toList
}
flip(r) {
for (l in 0...r) {
var t = _a[r]
_a[r] = _a[l]
_a[l] = t
r = r - 1
}
}
sort() {
for (uns in _a.count-1..1) {
var h = Find.highest(_a[0..uns])
var lx = h[2][0]
flip(lx)
flip(uns)
}
}
toString { _a.toString }
}
var p = Pancake.new([31, 41, 59, 26, 53, 58, 97, 93, 23, 84]) System.print("unsorted: %(p)") p.sort() System.print("sorted : %(p)")</lang>
- Output:
unsorted: [31, 41, 59, 26, 53, 58, 97, 93, 23, 84] sorted : [23, 26, 31, 41, 53, 58, 59, 84, 93, 97]
zkl
<lang zkl>fcn pancakeSort(a){
foreach i in ([a.len()-1..1,-1]){
j := a.index((0).max(a[0,i+1])); // min for decending sort
if(i != j){ a.swap(0,j); a.swap(0,i); }
}
a
}</lang> Note: [offset,count] not [start,stop]
Finding the max index creates a partial list, which isn't good; if it matters use: <lang zkl> j := (i+1).reduce('wrap(x,y){ if(a[x]>a[y]) x else y });</lang> <lang zkl>pancakeSort(List(7,6,9,2,4,8,1,3,5)).println();</lang>
- Output:
L(1,2,3,4,5,6,7,8,9)
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