Sattolo cycle

Sattolo cycle 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

Implement the   Sattolo cycle   for an integer array (or, if possible, an array of any type).

Sattolo cycle is use to shuffle an array ensuring each index is in a new position.

Related tasks

• Knuth shuffle

C#

<lang csharp>private static readonly Random Rand = new Random();

void sattoloCycle<T>(IList<T> items) {

   for (var i = items.Count; i-- > 1;) {
       int j = Rand.Next(i);
       var tmp = items[i];
       items[i] = items[j];
       items[j] = tmp;
   }

}</lang>

Java

<lang Java>private static final Random rng = new Random();

void sattoloCycle(Object[] items) {

   for (int i = items.length; i-- > 1;) {
       int j = rng.nextInt(i);
       Object tmp = items[i];
       items[i] = items[j];
       items[j] = tmp;
   }

}</lang>

JavaScript

<lang JavaScript>function sattoloCycle(items) {

   for (var i = items.length; i--> 1;) {
       var j = Math.floor(Math.random() * i);
       var tmp = items[i];
       items[i] = items[j];
       items[j] = tmp;
   }

}</lang>

Perl 6

This modifies the array passed as argument, in-place.

<lang perl6>sub sattolo-cycle (@array) {

   for reverse 1 .. @array.end -> $i {
       my $j = (^$i).pick;
       @array[$j, $i] = @array[$i, $j];
   }

}</lang>

Python

Copied from Wikipedia:

<lang python>from random import randrange

def sattoloCycle(items):

   i = len(items)
   while i > 1:
       i = i - 1
       j = randrange(i)  # 0 <= j <= i-1
       items[j], items[i] = items[i], items[j]
   return</lang>

TypeScript

<lang TypeScript>function sattoloCycle<T>(items: Array<T>): void {

   for (let i = items.length; i--> 1;) {
       const j = Math.floor(Math.random() * i);
       const tmp = items[i];
       items[i] = items[j];
       items[j] = tmp;
   }

}</lang>

zkl

<lang zkl>fcn sattoloCycle(list){ // in place

  foreach i in ([list.len()-1 .. 1,-1]){
     list.swap(i,(0).random(i));  # 0 <= j < i
  }
  list

}</lang> <lang zkl>sattoloCycle([0..9].walk().copy()).println(); sattoloCycle("this is a test".split()).println();</lang>

Output:

L(6,3,8,2,5,7,1,0,9,4)
L("test","this","is","a")