Last list item
List = [6, 81, 243, 14, 25, 49, 123, 69, 11]
Find the two smallest items, remove them from the list, find their sum, and add the sum to the end of list.
Repeat until the list contains one element.
Show the steps and last item on this page.
Show the unsorted list in output.
Last list item is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
- Task
ALGOL 68
<lang algol68>BEGIN # find the last element after repeatedely adding the sum #
# of the two smallest elements and removing them #
# Quicksorts in-place the array of integers a, from lb to ub #
PROC quicksort = ( REF[]INT a, INT lb, ub )VOID:
IF ub > lb THEN
# more than one element, so must sort #
INT left := lb;
INT right := ub;
# choosing the middle element of the array as the pivot #
INT pivot := a[ left + ( ( right + 1 ) - left ) OVER 2 ];
WHILE
WHILE IF left <= ub THEN a[ left ] < pivot ELSE FALSE FI DO left +:= 1 OD;
WHILE IF right >= lb THEN a[ right ] > pivot ELSE FALSE FI DO right -:= 1 OD;
left <= right
DO
INT t := a[ left ];
a[ left ] := a[ right ];
a[ right ] := t;
left +:= 1;
right -:= 1
OD;
quicksort( a, lb, right );
quicksort( a, left, ub )
FI # quicksort # ;
[ 1 : 9 ]INT a := ( 6, 81, 243, 14, 25, 49, 123, 69, 11 );
INT a count := UPB a;
WHILE a count > 1 DO
quicksort( a, LWB a, a count );
print( ( "Sorted list:" ) );FOR i TO a count DO print( ( " ", whole( a[ i ], 0 ) ) ) OD;
print( ( newline ) );
INT sum = a[ 1 ] + a[ 2 ];
print( ( "Two smallest: " , whole( a[ 1 ], 0 )
, " + ", whole( a[ 2 ], 0 )
, " = ", whole( sum, 0 )
, newline
)
);
a[ 2 ] := sum;
a[ 1 : a count - 1 ] := a[ 2 : a count ];
a count -:= 1
OD;
print( ( "Last item is ", whole( a[ 1 ], 0 ), ".", newline ) )
END</lang>
- Output:
Sorted list: 6 11 14 25 49 69 81 123 243 Two smallest: 6 + 11 = 17 Sorted list: 14 17 25 49 69 81 123 243 Two smallest: 14 + 17 = 31 Sorted list: 25 31 49 69 81 123 243 Two smallest: 25 + 31 = 56 Sorted list: 49 56 69 81 123 243 Two smallest: 49 + 56 = 105 Sorted list: 69 81 105 123 243 Two smallest: 69 + 81 = 150 Sorted list: 105 123 150 243 Two smallest: 105 + 123 = 228 Sorted list: 150 228 243 Two smallest: 150 + 228 = 378 Sorted list: 243 378 Two smallest: 243 + 378 = 621 Last item is 621.
C
<lang c>#include <stdio.h>
- include <stdlib.h>
int compare(const void *a, const void *b) {
int aa = *(const int *)a; int bb = *(const int *)b; if (aa < bb) return -1; if (aa > bb) return 1; return 0;
}
int main() {
int a[] = {6, 81, 243, 14, 25, 49, 123, 69, 11};
int isize = sizeof(int);
int asize = sizeof(a) / isize;
int i, sum;
while (asize > 1) {
qsort(a, asize, isize, compare);
printf("Sorted list: ");
for (i = 0; i < asize; ++i) printf("%d ", a[i]);
printf("\n");
sum = a[0] + a[1];
printf("Two smallest: %d + %d = %d\n", a[0], a[1], sum);
for (i = 2; i < asize; ++i) a[i-2] = a[i];
a[asize - 2] = sum;
asize--;
}
printf("Last item is %d.\n", a[0]);
return 0;
}</lang>
- Output:
Sorted list: 6 11 14 25 49 69 81 123 243 Two smallest: 6 + 11 = 17 Sorted list: 14 17 25 49 69 81 123 243 Two smallest: 14 + 17 = 31 Sorted list: 25 31 49 69 81 123 243 Two smallest: 25 + 31 = 56 Sorted list: 49 56 69 81 123 243 Two smallest: 49 + 56 = 105 Sorted list: 69 81 105 123 243 Two smallest: 69 + 81 = 150 Sorted list: 105 123 150 243 Two smallest: 105 + 123 = 228 Sorted list: 150 228 243 Two smallest: 150 + 228 = 378 Sorted list: 243 378 Two smallest: 243 + 378 = 621 Last item is 621.
Factor
<lang factor>USING: formatting io kernel math math.statistics prettyprint sequences sequences.extras ;
- list. ( seq -- )
"List: " write [ bl ] [ pprint ] interleave nl ;
- smallest. ( seq -- )
first2 2dup + "Two smallest: %d + %d = %d\n" printf ;
- remove-all-first! ( seq elts -- seq' )
[ swap remove-first! ] each ;
- step ( seq -- seq' )
dup { 0 1 } kth-smallests tuck remove-all-first! over
smallest. swap sum suffix! ;
V{ 6 81 243 14 25 49 123 69 11 } [ dup length 1 > ] [ dup list. step ] while last "Last item is %d.\n" printf</lang>
- Output:
List: 6 81 243 14 25 49 123 69 11 Two smallest: 6 + 11 = 17 List: 81 243 14 25 49 123 69 17 Two smallest: 14 + 17 = 31 List: 81 243 25 49 123 69 31 Two smallest: 25 + 31 = 56 List: 81 243 49 123 69 56 Two smallest: 49 + 56 = 105 List: 81 243 123 69 105 Two smallest: 69 + 81 = 150 List: 243 123 105 150 Two smallest: 105 + 123 = 228 List: 243 150 228 Two smallest: 150 + 228 = 378 List: 243 378 Two smallest: 243 + 378 = 621 Last item is 621.
Go
With sorting
<lang go>package main
import (
"fmt" "sort"
)
func main() {
a := []int{6, 81, 243, 14, 25, 49, 123, 69, 11}
for len(a) > 1 {
sort.Ints(a)
fmt.Println("Sorted list:", a)
sum := a[0] + a[1]
fmt.Printf("Two smallest: %d + %d = %d\n", a[0], a[1], sum)
a = append(a, sum)
a = a[2:]
}
fmt.Println("Last item is", a[0], "\b.")
}</lang>
- Output:
Sorted list: [6 11 14 25 49 69 81 123 243] Two smallest: 6 + 11 = 17 Sorted list: [14 17 25 49 69 81 123 243] Two smallest: 14 + 17 = 31 Sorted list: [25 31 49 69 81 123 243] Two smallest: 25 + 31 = 56 Sorted list: [49 56 69 81 123 243] Two smallest: 49 + 56 = 105 Sorted list: [69 81 105 123 243] Two smallest: 69 + 81 = 150 Sorted list: [105 123 150 243] Two smallest: 105 + 123 = 228 Sorted list: [150 228 243] Two smallest: 150 + 228 = 378 Sorted list: [243 378] Two smallest: 243 + 378 = 621 Last item is 621.
Without sorting
<lang go>package main
import "fmt"
func findMin(a []int) (int, int) {
ix := 0
min := a[0]
for i := 1; i < len(a); i++ {
if a[i] < min {
ix = i
min = a[i]
}
}
return min, ix
}
func main() {
a := []int{6, 81, 243, 14, 25, 49, 123, 69, 11}
for len(a) > 1 {
fmt.Println("List:", a)
var s [2]int
for i := 0; i < 2; i++ {
min, ix := findMin(a)
s[i] = min
a = append(a[:ix], a[ix+1:]...)
}
sum := s[0] + s[1]
fmt.Printf("Two smallest: %d + %d = %d\n", s[0], s[1], sum)
a = append(a, sum)
}
fmt.Println("Last item is", a[0], "\b.")
}</lang>
- Output:
List: [6 81 243 14 25 49 123 69 11] Two smallest: 6 + 11 = 17 List: [81 243 14 25 49 123 69 17] Two smallest: 14 + 17 = 31 List: [81 243 25 49 123 69 31] Two smallest: 25 + 31 = 56 List: [81 243 49 123 69 56] Two smallest: 49 + 56 = 105 List: [81 243 123 69 105] Two smallest: 69 + 81 = 150 List: [243 123 105 150] Two smallest: 105 + 123 = 228 List: [243 150 228] Two smallest: 150 + 228 = 378 List: [243 378] Two smallest: 243 + 378 = 621 Last item is 621.
Raku
Uses no sorting; does not modify overall list order while processing. <lang perl6>say ' Original ', my @list = 6, 81, 243, 14, 25, 49, 123, 69, 11;
say push @list: get(min @list) + get(min @list) while @list > 1;
sub get ($min) {
@list.splice: @list.first(* == $min, :k), 1; printf " %3d ", $min; $min;
}</lang>
- Output:
Original [6 81 243 14 25 49 123 69 11] 6 11 [81 243 14 25 49 123 69 17] 14 17 [81 243 25 49 123 69 31] 25 31 [81 243 49 123 69 56] 49 56 [81 243 123 69 105] 69 81 [243 123 105 150] 105 123 [243 150 228] 150 228 [243 378] 243 378 [621]
Ring
<lang ring> see "working..." + nl
List = [6,81,243,14,25,49,123,69,11] Temp = [] n = 0 while true
n++
Temp = sort(List)
first = Temp[1]
second = Temp[2]
ind1 = find(List,first)
ind2 = find(List,second)
if ind1 < ind2
del(List,ind2)
del(List,ind1)
else
del(List,ind1)
del(List,ind2)
ok
sum = first + second
add(List,sum)
if len(List) = 1
exit
ok
if n = 1
see nl + "List = "
showArray(List)
see nl
ok
showList(first,second,sum,List)
end
see "Last item is: " +List[1] + nl see "done..." + nl
func showList(first,second,sum,List)
see "two smallest is = " + first + " + " + second + " = " + sum + nl
see "List = "
showArray(List)
func showArray(array)
txt = ""
see "["
for n = 1 to len(array)
txt = txt + array[n] + ","
next
txt = left(txt,len(txt)-1)
txt = txt + "]"
see txt + nl
</lang>
- Output:
working... List = [81,243,14,25,49,123,69,17] two smallest is = 6 + 11 = 17 List = [81,243,14,25,49,123,69,17] two smallest is = 14 + 17 = 31 List = [81,243,25,49,123,69,31] two smallest is = 25 + 31 = 56 List = [81,243,49,123,69,56] two smallest is = 49 + 56 = 105 List = [81,243,123,69,105] two smallest is = 69 + 81 = 150 List = [243,123,105,150] two smallest is = 105 + 123 = 228 List = [243,150,228] two smallest is = 150 + 228 = 378 List = [243,378] Last item is: 621 done...
Wren
With sorting
<lang ecmascript>var a = [6, 81, 243, 14, 25, 49, 123, 69, 11]
while (a.count > 1) {
a.sort()
System.print("Sorted list: %(a)")
var sum = a[0] + a[1]
System.print("Two smallest: %(a[0]) + %(a[1]) = %(sum)")
a.add(sum)
a = a[2..-1]
}
System.print("Last item is %(a[0]).")</lang>
- Output:
Sorted list: [6, 11, 14, 25, 49, 69, 81, 123, 243] Two smallest: 6 + 11 = 17 Sorted list: [14, 17, 25, 49, 69, 81, 123, 243] Two smallest: 14 + 17 = 31 Sorted list: [25, 31, 49, 69, 81, 123, 243] Two smallest: 25 + 31 = 56 Sorted list: [49, 56, 69, 81, 123, 243] Two smallest: 49 + 56 = 105 Sorted list: [69, 81, 105, 123, 243] Two smallest: 69 + 81 = 150 Sorted list: [105, 123, 150, 243] Two smallest: 105 + 123 = 228 Sorted list: [150, 228, 243] Two smallest: 150 + 228 = 378 Sorted list: [243, 378] Two smallest: 243 + 378 = 621 Last item is 621.
Without sorting
<lang ecmascript>var findMin = Fn.new { |a|
var ix = 0
var min = a[0]
for (i in 1...a.count) {
if (a[i] < min) {
ix = i
min = a[i]
}
}
return [min, ix]
}
var a = [6, 81, 243, 14, 25, 49, 123, 69, 11]
while (a.count > 1) {
System.print("List: %(a)")
var s = List.filled(2, 0)
for (i in 0..1) {
var m = findMin.call(a)
s[i] = m[0]
a.removeAt(m[1])
}
var sum = s[0] + s[1]
System.print("Two smallest: %(s[0]) + %(s[1]) = %(sum)")
a.add(sum)
}
System.print("Last item is %(a[0]).")</lang>
- Output:
List: [6, 81, 243, 14, 25, 49, 123, 69, 11] Two smallest: 6 + 11 = 17 List: [81, 243, 14, 25, 49, 123, 69, 17] Two smallest: 14 + 17 = 31 List: [81, 243, 25, 49, 123, 69, 31] Two smallest: 25 + 31 = 56 List: [81, 243, 49, 123, 69, 56] Two smallest: 49 + 56 = 105 List: [81, 243, 123, 69, 105] Two smallest: 69 + 81 = 150 List: [243, 123, 105, 150] Two smallest: 105 + 123 = 228 List: [243, 150, 228] Two smallest: 150 + 228 = 378 List: [243, 378] Two smallest: 243 + 378 = 621 Last item is 621.