Sorting algorithms/Strand 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
| This page uses content from Wikipedia. The original article was at Strand sort. The list of authors can be seen in the page history. As with Rosetta Code, the text of Wikipedia is available under the GNU FDL. (See links for details on variance) |
- Task
Implement the Strand sort.
This is a way of sorting numbers by extracting shorter sequences of already sorted numbers from an unsorted list.
AutoHotkey
<lang AutoHotkey>string = ( -2 0 -2 5 5 3 -1 -3 5 5 0 2 -4 4 2 ) string2 := string Loop { loop, parse, string, %A_space% { list := 1 = A_index ? A_loopfield : list StringSplit, k, list, %A_space%
if ( k%k0% <= A_loopfield ) && ( l != "" ) && ( A_index != 1 ) list := list . " " . A_loopfield
if ( k%k0% > A_loopfield ) list := A_loopfield . " " . list , index++ l := A_loopfield } if ( index = 0 ) { MsgBox % "unsorted:" string2 "`n Sorted:" list exitapp } string := list, list = "", index := 0 } esc::ExitApp</lang>outout<lang> unsorted:-2 0 -2 5 5 3 -1 -3 5 5 0 2 -4 4 2
Sorted:-4 -3 -2 -2 -1 0 0 2 2 3 4 5 5 5 5</lang>
C
Strand sort using singly linked list. C99, compiled with gcc -std=c99
<lang C>#include <stdio.h>
typedef struct node_t *node, node_t; struct node_t { int v; node next; }; typedef struct { node head, tail; } slist;
void push(slist *l, node e) { if (!l->head) l->head = e; if (l->tail) l->tail->next = e; l->tail = e; }
node removehead(slist *l) { node e = l->head; if (e) { l->head = e->next; e->next = 0; } return e; }
void join(slist *a, slist *b) { push(a, b->head); a->tail = b->tail; }
void merge(slist *a, slist *b) { slist r = {0}; while (a->head && b->head) push(&r, removehead(a->head->v <= b->head->v ? a : b));
join(&r, a->head ? a : b); *a = r; b->head = b->tail = 0; }
void sort(int *ar, int len) { node_t all[len];
// array to list for (int i = 0; i < len; i++) all[i].v = ar[i], all[i].next = i < len - 1 ? all + i + 1 : 0;
slist list = {all, all + len - 1}, rem, strand = {0}, res = {0};
for (node e = 0; list.head; list = rem) { rem.head = rem.tail = 0; while ((e = removehead(&list))) push((!strand.head || e->v >= strand.tail->v) ? &strand : &rem, e);
merge(&res, &strand); }
// list to array for (int i = 0; res.head; i++, res.head = res.head->next) ar[i] = res.head->v; }
void show(const char *title, int *x, int len) { printf("%s ", title); for (int i = 0; i < len; i++) printf("%3d ", x[i]); putchar('\n'); }
int main(void) { int x[] = {-2,0,-2,5,5,3,-1,-3,5,5,0,2,-4,4,2};
- define SIZE sizeof(x)/sizeof(int)
show("before sort:", x, SIZE); sort(x, sizeof(x)/sizeof(int)); show("after sort: ", x, SIZE);
return 0; }</lang>outout<lang>before sort: -2 0 -2 5 5 3 -1 -3 5 5 0 2 -4 4 2 after sort: -4 -3 -2 -2 -1 0 0 2 2 3 4 5 5 5 5</lang>
C++
<lang cpp>#include <list>
template <typename T> std::list<T> strandSort(std::list<T> lst) {
if (lst.size() <= 1)
return lst;
std::list<T> result;
std::list<T> sorted;
while (!lst.empty()) {
sorted.push_back(lst.front());
lst.pop_front();
for (typename std::list<T>::iterator it = lst.begin(); it != lst.end(); ) {
if (sorted.back() <= *it) {
sorted.push_back(*it);
it = lst.erase(it);
} else
it++;
}
result.merge(sorted);
}
return result;
}</lang>
Clojure
<lang Clojure>(ns rosettacode.strand-sort)
(defn merge-join
"Produces a globally sorted seq from two sorted seqables"
[[a & la :as all] [b & lb :as bll]]
(cond (nil? a) bll
(nil? b) all
(< a b) (cons a (lazy-seq (merge-join la bll)))
true (cons b (lazy-seq (merge-join all lb)))))
(defn unbraid
"Separates a sorted list from a sequence"
[u]
(when (seq u)
(loop [[x & xs] u
u []
s []
e x]
(if (nil? x)
[s u]
(if (>= x e)
(recur xs u (conj s x) x)
(recur xs (conj u x) s e))))))
(defn strand-sort
"http://en.wikipedia.org/wiki/Strand_sort" [s] (loop [[s u] (unbraid s) m nil] (if s (recur (unbraid u) (merge-join m s)) m)))
(strand-sort [1, 6, 3, 2, 1, 7, 5, 3])
- => (1 1 2 3 3 5 6 7)
</lang>
CMake
Only for lists of integers. <lang cmake># strand_sort(<output variable> [<value>...]) sorts a list of integers. function(strand_sort var)
# Strand sort moves elements from _ARGN_ to _answer_.
set(answer) # answer: a sorted list
while(DEFINED ARGN)
# Split _ARGN_ into two lists, _accept_ and _reject_.
set(accept) # accept: elements in sorted order
set(reject) # reject: all other elements
set(p)
foreach(e ${ARGN})
if(DEFINED p AND p GREATER ${e})
list(APPEND reject ${e})
else()
list(APPEND accept ${e})
set(p ${e})
endif()
endforeach(e)
# Prepare to merge _accept_ into _answer_. First, convert both lists
# into arrays, for better indexing: set(e ${answer${i}}) is faster
# than list(GET answer ${i} e).
set(la 0)
foreach(e ${answer})
math(EXPR la "${la} + 1")
set(answer${la} ${e})
endforeach(e)
set(lb 0)
foreach(e ${accept})
math(EXPR lb "${lb} + 1")
set(accept${lb} ${e})
endforeach(e)
# Merge _accept_ into _answer_.
set(answer)
set(ia 1)
set(ib 1)
while(NOT ia GREATER ${la}) # Iterate elements of _answer_.
set(ea ${answer${ia}})
while(NOT ib GREATER ${lb}) # Take elements from _accept_,
set(eb ${accept${ib}}) # while they are less than
if(eb LESS ${ea}) # next element of _answer_.
list(APPEND answer ${eb})
math(EXPR ib "${ib} + 1")
else()
break()
endif()
endwhile()
list(APPEND answer ${ea}) # Take next from _answer_.
math(EXPR ia "${ia} + 1")
endwhile()
while(NOT ib GREATER ${lb}) # Take rest of _accept_.
list(APPEND answer ${accept${ib}})
math(EXPR ib "${ib} + 1")
endwhile()
# This _reject_ becomes next _ARGN_. If _reject_ is empty, then
# set(ARGN) undefines _ARGN_, breaking the loop.
set(ARGN ${reject})
endwhile(DEFINED ARGN)
set("${var}" ${answer} PARENT_SCOPE)
endfunction(strand_sort)</lang>
<lang cmake>strand_sort(result 11 55 55 44 11 33 33 44 22 22) message(STATUS "${result}") # -- 11;11;22;22;33;33;44;44;55;55</lang>
Common Lisp
<lang lisp>(defun strand-sort (l cmp)
(if l (let* ((l (reverse l))
(o (list (car l))) n)
(loop for i in (cdr l) do
(push i (if (funcall cmp (car o) i) n o)))
(merge 'list o (strand-sort n cmp) #'<))))
(let ((r (loop repeat 15 collect (random 10))))
(print r) (print (strand-sort r #'<)))</lang>output<lang>(5 8 6 0 6 8 4 7 0 7 1 5 3 3 6)
(0 0 1 3 3 4 5 5 6 6 6 7 7 8 8)</lang>
D
Using doubly linked lists
<lang d>import std.stdio, std.container;
DList!T strandSort(T)(DList!T list) {
static DList!T merge(DList!T left, DList!T right) {
DList!T result;
while (!left.empty && !right.empty) {
if (left.front <= right.front) {
result.insertBack(left.front);
left.removeFront();
} else {
result.insertBack(right.front);
right.removeFront();
}
}
result.insertBack(left[]);
result.insertBack(right[]);
return result;
}
DList!T result, sorted, leftover;
while (!list.empty) {
leftover.clear();
sorted.clear();
sorted.insertBack(list.front);
list.removeFront();
foreach (item; list) {
if (sorted.back <= item)
sorted.insertBack(item);
else
leftover.insertBack(item);
}
result = merge(sorted, result);
list = leftover;
}
return result;
}
void main() {
auto lst = DList!int([-2,0,-2,5,5,3,-1,-3,5,5,0,2,-4,4,2]);
foreach (e; strandSort(lst))
write(e, " ");
}</lang>
- Output:
-4 -3 -2 -2 -1 0 0 2 2 3 4 5 5 5 5
Faster version using slices
<lang d>import std.stdio, std.array;
T[] strandSort(T)(const(T)[] list) pure nothrow {
static T[] merge(const(T)[] left, const(T)[] right) pure nothrow {
T[] res;
while (!left.empty && !right.empty) {
if (left.front <= right.front) {
res ~= left.front;
left.popFront;
} else {
res ~= right.front;
right.popFront;
}
}
return res ~ left ~ right;
}
T[] result;
while (!list.empty) {
auto sorted = list[0 .. 1];
list.popFront;
typeof(sorted) leftover;
foreach (const item; list)
(sorted.back <= item ? sorted : leftover) ~= item;
result = merge(sorted, result);
list = leftover;
}
return result;
}
void main() {
const arr = [-2, 0, -2, 5, 5, 3, -1, -3, 5, 5, 0, 2, -4, 4, 2]; arr.strandSort.writeln;
}</lang>
- Output:
[-4, -3, -2, -2, -1, 0, 0, 2, 2, 3, 4, 5, 5, 5, 5]
Elixir
<lang elixir>defmodule Sort do
def strand_sort(args), do: strand_sort(args, [])
defp strand_sort([], result), do: result
defp strand_sort(a, result) do
{_, sublist, b} = Enum.reduce(a, {hd(a),[],[]}, fn val,{v,l1,l2} ->
if v <= val, do: {val, [val | l1], l2},
else: {v, l1, [val | l2]}
end)
strand_sort(b, :lists.merge(Enum.reverse(sublist), result))
end
end
IO.inspect Sort.strand_sort [7, 17, 6, 20, 20, 12, 1, 1, 9]</lang>
- Output:
[1, 1, 6, 7, 9, 12, 17, 20, 20]
Euphoria
<lang euphoria>function merge(sequence left, sequence right)
sequence result
result = {}
while length(left) > 0 and length(right) > 0 do
if left[$] <= right[1] then
exit
elsif right[$] <= left[1] then
return result & right & left
elsif left[1] < right[1] then
result = append(result,left[1])
left = left[2..$]
else
result = append(result,right[1])
right = right[2..$]
end if
end while
return result & left & right
end function
function strand_sort(sequence s)
integer j
sequence result
result = {}
while length(s) > 0 do
j = length(s)
for i = 1 to length(s)-1 do
if s[i] > s[i+1] then
j = i
exit
end if
end for
result = merge(result,s[1..j])
s = s[j+1..$]
end while
return result
end function
constant s = rand(repeat(1000,10)) puts(1,"Before: ") ? s puts(1,"After: ") ? strand_sort(s)</lang>
Output:
Before: {551,746,940,903,51,18,346,417,340,502}
After: {18,51,340,346,417,502,551,746,903,940}
Go
<lang go>package main
import "fmt"
type link struct {
int next *link
}
func linkInts(s []int) *link {
if len(s) == 0 {
return nil
}
return &link{s[0], linkInts(s[1:])}
}
func (l *link) String() string {
if l == nil {
return "nil"
}
r := fmt.Sprintf("[%d", l.int)
for l = l.next; l != nil; l = l.next {
r = fmt.Sprintf("%s %d", r, l.int)
}
return r + "]"
}
func main() {
a := linkInts([]int{170, 45, 75, -90, -802, 24, 2, 66})
fmt.Println("before:", a)
b := strandSort(a)
fmt.Println("after: ", b)
}
func strandSort(a *link) (result *link) {
for a != nil {
// build sublist
sublist := a
a = a.next
sTail := sublist
for p, pPrev := a, a; p != nil; p = p.next {
if p.int > sTail.int {
// append to sublist
sTail.next = p
sTail = p
// remove from a
if p == a {
a = p.next
} else {
pPrev.next = p.next
}
} else {
pPrev = p
}
}
sTail.next = nil // terminate sublist
if result == nil {
result = sublist
continue
}
// merge
var m, rr *link
if sublist.int < result.int {
m = sublist
sublist = m.next
rr = result
} else {
m = result
rr = m.next
}
result = m
for {
if sublist == nil {
m.next = rr
break
}
if rr == nil {
m.next = sublist
break
}
if sublist.int < rr.int {
m.next = sublist
m = sublist
sublist = m.next
} else {
m.next = rr
m = rr
rr = m.next
}
}
}
return
}</lang> Output:
before: [170 45 75 -90 -802 24 2 66] after: [-802 -90 2 24 45 66 75 170]
Haskell
<lang haskell>-- Same merge as in Merge Sort merge :: (Ord a) => [a] -> [a] -> [a] merge [] ys = ys merge xs [] = xs merge (x : xs) (y : ys) | x <= y = x : merge xs (y : ys) | otherwise = y : merge (x : xs) ys
strandSort :: (Ord a) => [a] -> [a] strandSort [] = [] strandSort (x : xs) = merge strand (strandSort rest) where (strand, rest) = extractStrand x xs extractStrand x [] = ([x], []) extractStrand x (x1 : xs) | x <= x1 = let (strand, rest) = extractStrand x1 xs in (x : strand, rest) | otherwise = let (strand, rest) = extractStrand x xs in (strand, x1 : rest)</lang>
J
Using merge defined at Sorting algorithms/Merge sort#J:
<lang j>strandSort=: (#~ merge $:^:(0<#)@(#~ -.)) (= >./\)</lang>
Example use:
<lang j> strandSort 3 1 5 4 2 1 2 3 4 5</lang>
Note: the order in which this J implementation processes the strands differs from the pseudocode currently at the wikipedia page on strand sort and matches the haskell implementation currently at the wikipedia page.
Also note that the individual strands can be seen by using ; instead of merge.
<lang j> ((#~ ; $:^:(0<#)@(#~ -.)) (= >./\)) 3 1 5 4 2 ┌───┬───┬─┬┐ │3 5│1 4│2││ └───┴───┴─┴┘
((#~ ; $:^:(0<#)@(#~ -.)) (= >./\)) 3 3 1 2 4 3 5 6
┌─────────┬─────┬┐ │3 3 4 5 6│1 2 3││ └─────────┴─────┴┘</lang>
Java
<lang java5>import java.util.Arrays; import java.util.LinkedList;
public class Strand{ // note: the input list is destroyed public static <E extends Comparable<? super E>> LinkedList<E> strandSort(LinkedList<E> list){ if(list.size() <= 1) return list;
LinkedList<E> result = new LinkedList<E>(); while(list.size() > 0){ LinkedList<E> sorted = new LinkedList<E>(); sorted.add(list.removeFirst()); //same as remove() or remove(0) for(Iterator<E> it = list.iterator(); it.hasNext(); ){ E elem = it.next(); if(sorted.peekLast().compareTo(elem) <= 0){ sorted.addLast(elem); //same as add(elem) or add(0, elem) it.remove(); } } result = merge(sorted, result); } return result; }
private static <E extends Comparable<? super E>> LinkedList<E> merge(LinkedList<E> left, LinkedList<E> right){ LinkedList<E> result = new LinkedList<E>(); while(!left.isEmpty() && !right.isEmpty()){ //change the direction of this comparison to change the direction of the sort if(left.peek().compareTo(right.peek()) <= 0) result.add(left.remove()); else result.add(right.remove()); } result.addAll(left); result.addAll(right); return result; }
public static void main(String[] args){ System.out.println(strandSort(new LinkedList<Integer>(Arrays.asList(3,1,2,4,5)))); System.out.println(strandSort(new LinkedList<Integer>(Arrays.asList(3,3,1,2,4,5)))); System.out.println(strandSort(new LinkedList<Integer>(Arrays.asList(3,3,1,2,4,3,5,6)))); } }</lang> Output:
[1, 2, 3, 4, 5] [1, 2, 3, 3, 4, 5] [1, 2, 3, 3, 3, 4, 5, 6]
jq
Most of the implementation is the "merge" function for merging two arrays. Notice that the helper function, strand, is defined here as an inner function.<lang jq># merge input array with array x by comparing the heads of the arrays
- in turn; # if both arrays are sorted, the result will be sorted:
def merge(x):
length as $length
| (x|length) as $xl
| if $length == 0 then x
elif $xl == 0 then .
else
. as $in
| reduce range(0; $xl + $length) as $z
# state [ix, xix, ans]
( [0, 0, []];
if .[0] < $length and
((.[1] < $xl and $in[.[0]] <= x[.[1]]) or .[1] == $xl)
then [(.[0] + 1), .[1], (.[2] + [$in[.[0]]]) ]
else [.[0], (.[1] + 1), (.[2] + [x[.[1]]]) ]
end
) | .[2]
end ;
def strand_sort:
# The inner function emits [strand, remainder]
def strand:
if length <= 1 then .
else
reduce .[] as $x
# state: [strand, remainder]
([ [], [] ];
if ((.[0]|length) == 0) or .[0][-1] <= $x
then [ (.[0] + [$x]), .[1] ]
else [ .[0], (.[1] + [$x]) ]
end )
end ;
if length <= 1 then . else strand as $s | ($s[0] | merge( $s[1] | strand_sort)) end ;
</lang> Example:
[1,3,5,2,4,6] | strand_sort
Julia
<lang julia>function mergelist(a, b)
out = Vector{Int}()
while !isempty(a) && !isempty(b)
if a[1] < b[1]
push!(out, popfirst!(a))
else
push!(out, popfirst!(b))
end
end
append!(out, a)
append!(out, b)
out
end
function strand(a)
i, s = 1, [popfirst!(a)]
while i < length(a) + 1
if a[i] > s[end]
append!(s, splice!(a, i))
else
i += 1
end
end
s
end
strandsort(a) = (out = strand(a); while !isempty(a) out = mergelist(out, strand(a)) end; out)
println(strandsort([1, 6, 3, 2, 1, 7, 5, 3]))
</lang>
- Output:
[1, 1, 2, 3, 3, 5, 6, 7]
Kotlin
<lang scala>// version 1.1.2
fun <T : Comparable<T>> strandSort(l: List<T>): List<T> {
fun merge(left: MutableList<T>, right: MutableList<T>): MutableList<T> {
val res = mutableListOf<T>()
while (!left.isEmpty() && !right.isEmpty()) {
if (left[0] <= right[0]) {
res.add(left[0])
left.removeAt(0)
}
else {
res.add(right[0])
right.removeAt(0)
}
}
res.addAll(left)
res.addAll(right)
return res
}
var list = l.toMutableList()
var result = mutableListOf<T>()
while (!list.isEmpty()) {
val sorted = mutableListOf(list[0])
list.removeAt(0)
val leftover = mutableListOf<T>()
for (item in list) {
if (sorted.last() <= item)
sorted.add(item)
else
leftover.add(item)
}
result = merge(sorted, result)
list = leftover
}
return result
}
fun main(args: Array<String>) {
val l = listOf(-2, 0, -2, 5, 5, 3, -1, -3, 5, 5, 0, 2, -4, 4, 2) println(strandSort(l))
}</lang>
- Output:
[-4, -3, -2, -2, -1, 0, 0, 2, 2, 3, 4, 5, 5, 5, 5]
Mathematica
<lang Mathematica>StrandSort[ input_ ] := Module[ {results = {}, A = input}, While[Length@A > 0,
sublist = {A1}; A = A2;;All;
For[i = 1, i < Length@A, i++,
If[ Ai > Last@sublist, AppendTo[sublist, Ai]; A = Delete[A, i];]
];
results = #Ordering@#&@Join[sublist, results];];
results ]</lang> Example usage :
StrandSort[{2, 3, 7, 5, 1, 4, 7}]
{1, 2, 3, 4, 5, 7, 7}
MAXScript
<lang MAXScript>fn strandSort arr = ( arr = deepcopy arr local sub = #() local results = #() while arr.count > 0 do ( sub = #() append sub (amax arr) deleteitem arr (for i in 1 to arr.count where arr[i] == amax arr collect i)[1] local i = 1 while i <= arr.count do ( if arr[i] > sub[sub.count] do ( append sub arr[i] deleteitem arr i ) i += 1 ) results = join sub results ) return results
)</lang> Output: <lang MAXScript> a = for i in 1 to 20 collect random 1 40
- (19, 26, 14, 31, 11, 33, 2, 14, 32, 28, 12, 38, 2, 37, 27, 18, 31, 24, 39, 28)
strandSort a
- (2, 2, 11, 12, 14, 14, 18, 19, 24, 26, 27, 28, 28, 31, 31, 32, 33, 37, 38, 39)
</lang>
NetRexx
<lang NetRexx>/* NetRexx */ options replace format comments java crossref savelog symbols binary
import java.util.List
placesList = [String -
"UK London", "US New York", "US Boston", "US Washington" - , "UK Washington", "US Birmingham", "UK Birmingham", "UK Boston" -
]
lists = [ -
placesList - , strandSort(String[] Arrays.copyOf(placesList, placesList.length)) -
]
loop ln = 0 to lists.length - 1
cl = lists[ln] loop ct = 0 to cl.length - 1 say cl[ct] end ct say end ln
return
method strandSort(A = String[]) public constant binary returns String[]
rl = String[A.length] al = List strandSort(Arrays.asList(A)) al.toArray(rl)
return rl
method strandSort(Alst = List) public constant binary returns ArrayList
A = ArrayList(Alst)
result = ArrayList()
loop label A_ while A.size > 0
sublist = ArrayList()
sublist.add(A.get(0))
A.remove(0)
loop i_ = 0 while i_ < A.size - 1
if (Comparable A.get(i_)).compareTo(Comparable sublist.get(sublist.size - 1)) > 0 then do
sublist.add(A.get(i_))
A.remove(i_)
end
end i_
result = merge(result, sublist)
end A_
return result
method merge(left = List, right = List) public constant binary returns ArrayList
result = ArrayList()
loop label mx while left.size > 0 & right.size > 0
if (Comparable left.get(0)).compareTo(Comparable right.get(0)) <= 0 then do
result.add(left.get(0))
left.remove(0)
end
else do
result.add(right.get(0))
right.remove(0)
end
end mx
if left.size > 0 then do
result.addAll(left)
end
if right.size > 0 then do
result.addAll(right)
end
return result
</lang>
- Output
UK London US New York US Boston US Washington UK Washington US Birmingham UK Birmingham UK Boston UK Birmingham UK Boston UK London UK Washington US Birmingham US Boston US New York US Washington
Nim
<lang nim>proc mergeList[T](a, b: var seq[T]): seq[T] =
result = @[]
while a.len > 0 and b.len > 0:
if a[0] < b[0]:
result.add a[0]
a.delete 0
else:
result.add b[0]
b.delete 0
result.add a
result.add b
proc strand[T](a: var seq[T]): seq[T] =
var i = 0
result = @[a[0]]
a.delete 0
while i < a.len:
if a[i] > result[result.high]:
result.add a[i]
a.delete i
else:
inc i
proc strandSort[T](a: seq[T]): seq[T] =
var a = a result = a.strand while a.len > 0: var s = a.strand result = mergeList(result, s)
var a = @[1, 6, 3, 2, 1, 7, 5, 3] echo a.strandSort</lang> Output:
@[1, 1, 2, 3, 3, 5, 6, 7]
OCaml
<lang ocaml>let rec strand_sort (cmp : 'a -> 'a -> int) : 'a list -> 'a list = function
[] -> []
| x::xs ->
let rec extract_strand x = function
[] -> [x], []
| x1::xs when cmp x x1 <= 0 ->
let strand, rest = extract_strand x1 xs in x::strand, rest
| x1::xs ->
let strand, rest = extract_strand x xs in strand, x1::rest
in
let strand, rest = extract_strand x xs in
List.merge cmp strand (strand_sort cmp rest)</lang>
usage
# strand_sort compare [170; 45; 75; -90; -802; 24; 2; 66];; - : int list = [-802; -90; 2; 24; 45; 66; 75; 170]
PARI/GP
<lang parigp>strandSort(v)={ my(sorted=[],unsorted=v,remaining,working); while(#unsorted, remaining=working=List(); listput(working, unsorted[1]); for(i=2,#unsorted, if(unsorted[i]<working[#working], listput(remaining, unsorted[i]) , listput(working, unsorted[i]) ) ); unsorted=Vec(remaining); sorted=merge(sorted, Vec(working)) ); sorted }; merge(u,v)={ my(ret=vector(#u+#v),i=1,j=1); for(k=1,#ret, if(i<=#u & (j>#v | u[i]<v[j]), ret[k]=u[i]; i++ , ret[k]=v[j]; j++ ) ); ret };</lang>
Pascal
<lang Pascal>program StrandSortDemo;
type
TIntArray = array of integer;
function merge(left: TIntArray; right: TIntArray): TIntArray;
var
i, j, k: integer;
begin
setlength(merge, length(left) + length(right));
i := low(merge);
j := low(left);
k := low(right);
repeat
if ((left[j] <= right[k]) and (j <= high(left))) or (k > high(right)) then
begin
merge[i] := left[j];
inc(j);
end
else
begin
merge[i] := right[k];
inc(k);
end;
inc(i);
until i > high(merge);
end;
function StrandSort(s: TIntArray): TIntArray;
var
strand: TIntArray;
i, j: integer;
begin
setlength(StrandSort, length(s));
setlength(strand, length(s));
i := low(s);
repeat
StrandSort[i] := s[i];
inc(i);
until (s[i] < s[i-1]);
setlength(StrandSort, i);
repeat
setlength(strand, 1);
j := low(strand);
strand[j] := s[i];
while (s[i+1] > s[i]) and (i < high(s)) do
begin
inc(i);
inc(j);
setlength(strand, length(strand) + 1);
Strand[j] := s[i];
end;
StrandSort := merge(StrandSort, strand);
inc(i);
until (i > high(s));
end;
var
data: TIntArray; 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;
data := StrandSort(data);
writeln('The data after sorting:');
for i := low(data) to high(data) do
begin
write(data[i]:4);
end;
writeln;
end.</lang>
Perl
<lang Perl>use 5.10.0; # for given/when sub merge {
my ($x, $y) = @_;
my @out;
while (@$x and @$y) {
given ($x->[-1] <=> $y->[-1]) {
when( 1) { unshift @out, pop @$x }
when(-1) { unshift @out, pop @$y }
default { splice @out, 0, 0, pop(@$x), pop(@$y) }
}
}
return @$x, @$y, @out
}
sub strand {
my $x = shift;
my @out = shift @$x // return;
if (@$x) {
for (-@$x .. -1) {
if ($x->[$_] >= $out[-1]) {
push @out, splice @$x, $_, 1
}
}
}
return @out
}
sub strand_sort {
my @x = @_;
my @out;
while (my @strand = strand(\@x)) {
@out = merge(\@out, \@strand)
}
@out
}
my @a = map (int rand(100), 1 .. 10); say "Before @a"; @a = strand_sort(@a); say "After @a";</lang>
Perl 6
<lang perl6>sub infix:<M> (@x-in, @y-in) {
my @x = | @x-in;
my @y = | @y-in;
flat @x, @y,
reverse gather while @x and @y {
take do given @x[*-1] cmp @y[*-1] {
when More { pop @x }
when Less { pop @y }
when Same { pop(@x), pop(@y) }
}
}
}
sub strand (@x) {
my $i = 0;
my $prev = -Inf;
gather while $i < @x {
@x[$i] before $prev ?? $i++ !! take $prev = splice(@x, $i, 1)[0];
}
}
sub strand_sort (@x is copy) {
my @out; @out M= strand(@x) while @x; @out;
}
my @a = (^100).roll(10); say "Before {@a}"; @a = strand_sort(@a); say "After {@a}";
@a = <The quick brown fox jumps over the lazy dog>; say "Before {@a}"; @a = strand_sort(@a); say "After {@a}";</lang>
- Output:
Before 1 20 64 72 48 75 96 55 42 74 After 1 20 42 48 55 64 72 74 75 96 Before The quick brown fox jumps over the lazy dog After The brown dog fox jumps lazy over quick the
Phix
Copy of Euphoria <lang Phix>function merge(sequence left, sequence right) sequence result = {}
while length(left)>0 and length(right)>0 do
if left[$]<=right[1] then
exit
elsif right[$]<=left[1] then
return result & right & left
elsif left[1]<right[1] then
result = append(result,left[1])
left = left[2..$]
else
result = append(result,right[1])
right = right[2..$]
end if
end while
return result & left & right
end function
function strand_sort(sequence s) integer j sequence result = {}
while length(s)>0 do
j = length(s)
for i=1 to length(s)-1 do
if s[i]>s[i+1] then
j = i
exit
end if
end for
result = merge(result,s[1..j])
s = s[j+1..$]
end while
return result
end function</lang>
PHP
<lang php>$lst = new SplDoublyLinkedList(); foreach (array(1,20,64,72,48,75,96,55,42,74) as $v)
$lst->push($v);
foreach (strandSort($lst) as $v)
echo "$v ";
function strandSort(SplDoublyLinkedList $lst) {
$result = new SplDoublyLinkedList();
while (!$lst->isEmpty()) {
$sorted = new SplDoublyLinkedList();
$remain = new SplDoublyLinkedList();
$sorted->push($lst->shift());
foreach ($lst as $item) {
if ($sorted->top() <= $item) {
$sorted->push($item);
} else {
$remain->push($item);
}
}
$result = _merge($sorted, $result);
$lst = $remain;
}
return $result;
}
function _merge(SplDoublyLinkedList $left, SplDoublyLinkedList $right) {
$res = new SplDoublyLinkedList();
while (!$left->isEmpty() && !$right->isEmpty()) {
if ($left->bottom() <= $right->bottom()) {
$res->push($left->shift());
} else {
$res->push($right->shift());
}
}
foreach ($left as $v) $res->push($v);
foreach ($right as $v) $res->push($v);
return $res;
}</lang>
1 20 42 48 55 64 72 74 75 96
PicoLisp
<lang PicoLisp>(de strandSort (Lst)
(let Res NIL # Result list
(while Lst
(let Sub (circ (car Lst)) # Build sublist as fifo
(setq
Lst (filter
'((X)
(or
(> (car Sub) X)
(nil (fifo 'Sub X)) ) )
(cdr Lst) )
Res (make
(while (or Res Sub) # Merge
(link
(if2 Res Sub
(if (>= (car Res) (cadr Sub))
(fifo 'Sub)
(pop 'Res) )
(pop 'Res)
(fifo 'Sub) ) ) ) ) ) ) )
Res ) )</lang>
Test:
: (strandSort (3 1 5 4 2)) -> (1 2 3 4 5) : (strandSort (3 abc 1 (d e f) 5 T 4 NIL 2)) -> (NIL 1 2 3 4 5 abc (d e f) T)
PL/I
<lang PL/I>strand: procedure options (main); /* 27 Oct. 2012 */
declare A(100) fixed, used(100) bit (1), sorted fixed controlled; declare (temp, work) fixed controlled; declare (i, j, k, n) fixed binary;
n = hbound(A, 1); used = '1'b; A = random()*99;
put edit (A) (f(3));
do while (allocation(sorted) < n);
call fetch (A, work);
call move (temp, work);
call merge(sorted, temp);
/* Merges elements in SORTED with elements in TEMP. */
end;
/* Transfer the sorted elements to A. */
do i = 1 to allocation(sorted);
A(i) = sorted; free sorted;
end;
/* Print the sorted values. */
put skip list ('The sorted values are:');
put skip edit (A) (f(3));
/* Merges elements of SORTED with elements of TEMP and places */ /* the result in SORTED. */ /* Elements in SORTED and TEMP are in forward order. */ merge: procedure (sorted, temp);
declare (sorted, temp) fixed controlled; declare work fixed controlled; declare (j_ok, k_ok) bit (1);
do until ((k_ok | j_ok) = '0'b);
k_ok = allocation(sorted) > 0;
j_ok = allocation(temp) > 0;
if k_ok & j_ok then
do;
if sorted <= temp then
do; allocate work; work = sorted; free sorted; end;
else
do; allocate work; work = temp; free temp; end;
end;
else
if allocation(temp) = 0 then
/* temp is empty; copy remainder of sorted into work */
do while (allocation(sorted) > 0);
allocate work; work = sorted; free sorted;
end;
else
/* sorted is empty; copy remainder of temp onto work */
do while (allocation(temp) > 0);
allocate work; work = temp; free temp;
end;
end;
call move (sorted, work); /* Move the values to SORTED. */
end merge;
/* Collect a thread of ascending values from aray A, and stack them in temp. */ /* Note: the values in temp are in reverse order. */ fetch: procedure (A, temp);
declare A(*) fixed, temp controlled fixed;
declare i fixed binary;
do i = 1 to hbound(A,1);
if used(i) then
do; allocate temp; temp = A(i); used(i) = '0'b; go to found; end;
end;
found:
do i = i+1 to hbound(A,1);
if (temp <= A(i)) & used(i) then
do; allocate temp; temp = A(i); used(i) = '0'b; end;
end;
end fetch;
/* Copy the stack at TEMP to the stack at SORTED. */ /* In TEMP, elements are in reverse order; */ /* in SORTED, elements are in forward order. */ move: procedure (sorted, temp);
declare (sorted, temp) fixed controlled;
do while (allocation(sorted) > 0); free sorted; end;
do while (allocation (temp) > 0);
allocate sorted; sorted = temp; free temp;
end;
end move;
end strand;</lang> Generated data:
43 5 79 16 90 48 29 73 29 19 77 59 49 2 54 35 39 71 25 76 34 48 31 91 28 13 23 70 27 59 96 7 63 82 59 81 28 96 34 43 81 98 21 47 72 57 45 64 94 51 18 11 65 12 61 97 13 84 95 89 43 8 14 31 58 68 58 39 59 26 72 38 26 85 30 89 42 90 29 11 14 63 97 60 1 17 45 42 62 29 45 15 69 11 29 25 11 48 92 3
Results:
The sorted values are: 1 2 3 5 7 8 11 11 11 11 12 13 13 14 14 15 16 17 18 19 21 23 25 25 26 26 27 28 28 29 29 29 29 29 30 31 31 34 34 35 38 39 39 42 42 43 43 43 45 45 45 47 48 48 48 49 51 54 57 58 58 59 59 59 59 60 61 62 63 63 64 65 68 69 70 71 72 72 73 76 77 79 81 81 82 84 85 89 89 90 90 91 92 94 95 96 96 97 97 98
PureBasic
<lang PureBasic>Procedure strandSort(List a())
Protected NewList subList()
Protected NewList results()
While ListSize(a()) > 0
ClearList(subList())
AddElement(subList())
FirstElement(a())
subList() = a()
DeleteElement(a())
ForEach a()
If a() >= subList()
AddElement(subList())
subList() = a()
DeleteElement(a())
EndIf
Next
;merge lists
FirstElement(subList())
If Not FirstElement(results())
;copy all of sublist() to results()
MergeLists(subList(), results(), #PB_List_Last)
Else
Repeat
If subList() < results()
InsertElement(results())
results() = subList()
DeleteElement(subList())
If Not NextElement(subList())
Break
EndIf
ElseIf Not NextElement(results())
;add remainder of sublist() to end of results()
MergeLists(subList(), results(), #PB_List_Last)
Break
EndIf
ForEver
EndIf
Wend
CopyList(results(), a())
EndProcedure
Procedure.s listContents(List a())
Protected output.s PushListPosition(a()) ForEach a() output + Str(a()) + "," Next PopListPosition(a()) ProcedureReturn Left(output, Len(output) - 1)
EndProcedure
Procedure setupList(List a())
ClearList(a()) Protected elementCount, i elementCount = Random(5) + 10 For i = 1 To elementCount AddElement(a()) a() = Random(10) - 5 Next
EndProcedure
If OpenConsole()
NewList sample()
Define i
For i = 1 To 3
setupList(sample())
PrintN("List " + Str(i) + ":")
PrintN(" Before: " + listContents(sample()))
strandSort(sample())
PrintN(" After : " + listContents(sample()))
PrintN("")
Next
Print(#CRLF$ + #CRLF$ + "Press ENTER to exit"): Input()
CloseConsole()
EndIf</lang> Sample output:
List 1: Before: 3,-2,-4,4,-1,-3,-2,-2,2,2,0 After : -4,-3,-2,-2,-2,-1,0,2,2,3,4 List 2: Before: -4,4,3,-2,3,-2,5,0,-1,0,5,1 After : -4,-2,-2,-1,0,0,1,3,3,4,5,5 List 3: Before: -2,0,-2,5,5,3,-1,-3,5,5,0,2,-4,4,2 After : -4,-3,-2,-2,-1,0,0,2,2,3,4,5,5,5,5
Python
<lang Python>def merge_list(a, b): out = [] while len(a) and len(b): if a[0] < b[0]: out.append(a.pop(0)) else: out.append(b.pop(0)) out += a out += b return out
def strand(a): i, s = 0, [a.pop(0)] while i < len(a): if a[i] > s[-1]: s.append(a.pop(i)) else: i += 1 return s
def strand_sort(a): out = strand(a) while len(a): out = merge_list(out, strand(a)) return out
print strand_sort([1, 6, 3, 2, 1, 7, 5, 3])</lang> Output:<lang>[1, 1, 2, 3, 3, 5, 6, 7]</lang>
Racket
<lang racket>
- lang racket
(require mzlib/list) (define (merge xs ys) (merge-sorted-lists xs ys <=))
(define (strand-sort xs)
(let loop ([xs xs] [ys '[]])
(cond [(empty? xs) ys]
[else (define-values (sorted unsorted) (extract-strand xs))
(loop unsorted (merge sorted ys))])))
(define (extract-strand xs)
(for/fold ([strand '()] [unsorted '[]]) ([x xs])
(if (or (empty? strand) (< x (first strand)))
(values (cons x strand) unsorted)
(values strand (cons x unsorted)))))
(strand-sort (build-list 10 (λ(_) (random 15)))) </lang>
REXX
This REXX program was written to generate a specified amount of random numbers as well as allowing a pre-pended list of numbers).
It can handle integers, floating point numbers, exponentiated numbers, and/or character strings. <lang rexx>/*REXX program sorts a random list of words (or numbers) using the strand sort algorithm*/ parse arg size minv maxv old /*obtain optional arguments from the CL*/ if size== | size=="," then size=20 /*Not specified? Then use the default.*/ if minv== | minv=="," then minv= 0 /*Not specified? Then use the default.*/ if maxv== | maxv=="," then maxv=size /*Not specified? Then use the default.*/
do i=1 for size /*generate a list of random numbers. */
old=old random(0,maxv-minv)+minv /*append a random number to a list. */
end /*i*/
old=space(old) /*elide extraneous blanks from the list*/
say center('unsorted list', length(old), "─"); say old
new=strand_sort(old) /*sort the list of the random numbers. */ say; say center('sorted list' , length(new), "─"); say new exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ strand_sort: procedure; parse arg x; y=
do while words(x)\==0; w=words(x)
do j=1 for w-1 /*anything out of order?*/
if word(x,j)>word(x,j+1) then do; w=j; leave; end
end /*j*/
y=merge(y,subword(x,1,w)); x=subword(x,w+1)
end /*while*/
return y
/*──────────────────────────────────────────────────────────────────────────────────────*/ merge: procedure; parse arg a.1,a.2; p=
do forever; w1=words(a.1); w2=words(a.2) /*do while 2 lists exist*/
if w1==0 | if w2==0 then leave /*Any list empty? Stop.*/
if word(a.1,w1) <= word(a.2,1) then leave /*lists are now sorted? */
if word(a.2,w2) <= word(a.1,1) then return space(p a.2 a.1)
#=1+(word(a.1,1) >= word(a.2,1)); p=p word(a.#,1); a.#=subword(a.#,2)
end /*forever*/
return space(p a.1 a.2)</lang>
output when using the input of: 25 -9 30 1000 2000 3000
────────────────────────────────unsorted list──────────────────────────────── 1000 2000 3000 9 0 3 -8 17 8 -2 4 0 -3 19 -1 3 1 8 27 14 20 2 -6 23 1 -8 -4 4 ─────────────────────────────────sorted list───────────────────────────────── -8 -8 -6 -4 -3 -2 -1 0 0 1 1 2 3 3 4 4 8 8 9 14 17 19 20 23 27 1000 2000 3000
The REXX program can also sort words as well as numbers.
output when using the input of: 24 -9 100 66 66 8.8 carp Carp
──────────────────────────────────────unsorted list─────────────────────────────────────── 66 66 8.8 carp Carp 20 77 88 9 39 -5 10 12 80 87 26 61 87 94 73 27 49 35 95 81 76 40 13 72 ───────────────────────────────────────sorted list──────────────────────────────────────── -5 8.8 9 10 12 13 20 26 27 35 39 40 49 61 66 66 72 73 76 77 80 81 87 87 88 94 95 Carp carp
Note that an ASCII computer will sort words differently than an EBCDIC machine.
The order of sorting on an ASCII machine is: numbers, upperCase, lowerCase
The order of sorting on an EBCDIC machine is: lowerCase, upperCase, numbers
Ring
<lang ring>
- Project : Sorting algorithms/Strand sort
test = [-2,0,-2,5,5,3,-1,-3,5,5,0,2,-4,4,2] results = [] resultsend = [] see "before sort:" + nl showarray(test) test = strandsort(test) see "after sort:" + nl showarray(test)
func strandsort(a)
while len(a) > 0
sublist = []
add(sublist,a[1])
del(a,1)
for i = 1 to len(a)
if a[i] > sublist[len(sublist)]
add(sublist,a[i])
del(a,i)
ok
next
for n = 1 to len(sublist)
add(results,sublist[n])
next
for n = 1 to len(results)
for m = n + 1 to len(results)
if results[m] < results[n]
temp = results[m]
results[m] = results[n]
results[n] = temp
ok
next
next
end
return results
func showarray(vect)
svect = ""
for n = 1 to len(vect)
svect = svect + vect[n] + " "
next
svect = left(svect, len(svect) - 1)
see svect + nl
</lang> Output:
before sort: -2 0 -2 5 5 3 -1 -3 5 5 0 2 -4 4 2 after sort: -4 -3 -2 -2 -1 0 0 2 2 3 4 5 5 5 5
Ruby
<lang ruby>class Array
def strandsort
a = dup
result = []
until a.empty?
v = a.first
sublist, a = a.partition{|val| v=val if v<=val} # In case of v>val, it becomes nil.
result.each_index do |idx|
break if sublist.empty?
result.insert(idx, sublist.shift) if sublist.first < result[idx]
end
result += sublist
end
result
end
def strandsort!
replace(strandsort)
end
end
p [1, 6, 3, 2, 1, 7, 5, 3].strandsort</lang>
- Output:
[1, 1, 2, 3, 3, 5, 6, 7]
Sidef
<lang ruby>func merge(x, y) {
var out = [];
while (x && y) {
given (x[-1] <=> y[-1]) {
when ( 1) { out.prepend(x.pop) }
when (-1) { out.prepend(y.pop) }
default { out.prepend(x.pop, y.pop) }
}
}
x + y + out;
}
func strand(x) {
x || return [];
var out = [x.shift];
if (x.len) {
for i in (-x.len .. -1) {
if (x[i] >= out[-1]) {
out.append(x.pop_at(i));
}
}
}
return out;
}
func strand_sort(x) {
var out = [];
while (var strd = strand(x)) {
out = merge(out, strd);
}
return out;
}
var a = 10.of { 100.irand }; say "Before: #{a}"; say "After: #{strand_sort(a)}";</lang>
- Output:
Before: 24 62 29 95 11 21 46 3 23 20 After: 3 11 20 21 23 24 29 46 62 95
Tcl
<lang tcl>proc merge {listVar toMerge} {
upvar 1 $listVar v
set i [set j 0]
set out {}
while {$i<[llength $v] && $j<[llength $toMerge]} {
if {[set a [lindex $v $i]] < [set b [lindex $toMerge $j]]} { lappend out $a incr i } else { lappend out $b incr j }
} # Done the merge, but will be one source with something left # This will handle all that by doing a merge of the remnants onto the end set v [concat $out [lrange $v $i end] [lrange $toMerge $j end]] return
}
proc strandSort A {
set results {}
while {[llength $A]} {
set sublist [lrange $A 0 0] # We build a list of items that weren't filtered rather than removing "in place" # because this fits better with the way Tcl values work (the underlying data # structure is an array, not a linked list). set newA {} foreach a [lrange $A 1 end] { if {$a > [lindex $sublist end]} { lappend sublist $a } else { lappend newA $a } } set A $newA merge results $sublist
} return $results
}
puts [strandSort {3 1 5 4 2}]</lang>
Ursala
<lang Ursala>strand_sort "r" = # parameterized by a relational predicate "r"
@NiX -+
:-0 ~&B^?a\~&Y@a "r"?abh/~&alh2faltPrXPRC ~&arh2falrtPXPRC, ~&r->l ^|rlPlCrrPX/~& @hNCNXtX ~&r->lbx "r"?rllPXh/~&llPrhPlrPCXrtPX ~&rhPllPClrPXrtPX+-</lang>
demonstration code:<lang Ursala>#cast %nL
x = (strand_sort nat-nleq) <3,1,5,4,2></lang>output:
<1,2,3,4,5>
zkl
<lang zkl>fcn strandSort(A){ //--> new list, A is cleared, should add A=A.copy()
sublist:=List.createLong(A.len()); results:=List.createLong(A.len());
while(A){
sublist.clear(A.pop(0));
foreach i in (A.len() - 1){
if(A[i]>sublist[-1]) sublist.append(A.pop(i));
}
results.merge(sublist);
}
results
}</lang> The createLong list method creates a new list with pre-allocated space <lang zkl>strandSort(L(3,1,5,4,2)).println(); strandSort("azbfe".split("")).println();</lang>
- Output:
L(1,2,3,4,5)
L("a","b","e","f","z")