Sattolo cycle: Difference between revisions

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The Sattolo cycle is an algorithm for randomly shuffling an array in such a way that each element ends up in a new position.

Task

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

Specification

Given an array items with indices ranging from 0 to last, the algorithm can be defined as follows (pseudo-code):

for i from last downto 1 do:
    let j = random integer in range 0  $\leq$  j < i
    swap items[i] with items[j]

Notes:

It modifies the input array in-place. If that is unreasonable in your programming language, you may amend the algorithm to return the shuffled items as a new array instead.
The algorithm can also be amended to iterate from left to right, if that is more convenient.
The only difference between this and the Knuth shuffle, is that $j$ is chosen from the range 0 $\leq$ j < i, rather than 0 $\leq$ j $\leq$ i. This is what ensures that every element ends up in a new position, as long as there are at least two elements.

Test cases

Input array	Possible output arrays
`[]`	`[]`
`[10]`	`[10]`
`[10, 20]`	`[20, 10]`
`[10, 20, 30]`	`[20, 30, 10]` `[30, 10, 20]`
`[11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22]`	39,916,800 possibilities. You'll know you have a correct one if it has the same elements as the input array, but none in their original place.

Related tasks

Knuth shuffle

Other tasks related to string operations:

Metrics

Counting

Remove/replace

Anagrams/Derangements/shuffling

Find/Search/Determine

Formatting

Song lyrics/poems/Mad Libs/phrases

Tokenize

Sequences

11l

Translation of: Python

F sattolo_cycle(&items)
   L(i) (items.len-1 .. 1).step(-1)
      V j = random:(i)
      swap(&items[j], &items[i])

L 3
   V lst = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
   sattolo_cycle(&lst)
   print(lst)

Output:

[7, 1, 4, 8, 9, 2, 5, 6, 10, 3]
[3, 8, 9, 2, 1, 5, 4, 10, 7, 6]
[2, 9, 7, 5, 1, 3, 8, 10, 6, 4]

Action!

PROC PrintTable(INT ARRAY tab INT size)
  INT i

  Put('[)
  FOR i=0 TO size-1
  DO
    IF i>0 THEN Put(32) FI
    PrintI(tab(i))
  OD
  PrintE("]")
RETURN

PROC SattaloCycle(INT ARRAY tab INT size)
  INT i,j,tmp

  i=size-1
  WHILE i>0
  DO
    j=Rand(i)
    tmp=tab(i)
    tab(i)=tab(j)
    tab(j)=tmp
    i==-1
  OD
RETURN

PROC Test(INT ARRAY tab INT size)
  Print("Original data: ")
  PrintTable(tab,size)
  SattaloCycle(tab,size)
  Print("Shuffled data: ")
  PrintTable(tab,size)
  PutE()
RETURN

PROC Main()
  INT ARRAY a=[10 20 30],b=[11 12 13 14 15 16 17 18 19 20 21 22]

  Test(a,0)
  Test(a,1)
  Test(a,2)
  Test(a,3)
  Test(b,12)
RETURN

Output:

Screenshot from Atari 8-bit computer

Original data: []
Shuffled data: []

Original data: [10]
Shuffled data: [10]

Original data: [10 20]
Shuffled data: [20 10]

Original data: [20 10 30]
Shuffled data: [10 30 20]

Original data: [11 12 13 14 15 16 17 18 19 20 21 22]
Shuffled data: [21 22 19 15 18 12 13 16 14 11 17 20]

ALGOL 68

Arrays in Algol 68 need not have a lower bound of 0, other than that, this implements the pseudo code.

BEGIN
    # reorders the elements of a using the Sattolo cycle              #
    # this operates on integer arrays, additional SATTOLO operators   #
    # could be defined for other types                                #
    # a is returned so we can write e.g. SATTOLO SATTOLO a to cycle   #
    # the elements twice                                              #
    OP SATTOLO = ( REF[]INT a )REF[]INT:
       BEGIN
            REF[]INT aa := a[ @ 0 ];
            FOR i FROM UPB aa BY -1 TO 1 DO
                INT j    = ENTIER ( next random * i );
                INT t    = aa[ i ];
                aa[ i ] := aa[ j ];
                aa[ j ] := t
            OD;
            a
       END # SATTOLO # ;
    [ 1 : 10 ]INT a := []INT( 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 )[ @ 1 ];
    TO 5 DO
        SATTOLO a;
        FOR i FROM LWB a TO UPB a DO print( ( " ", whole( a[ i ], -3 ) ) ) OD;
        print( ( newline ) )
    OD
END

Output:

   4   9   2   5   3   1   8  10   7   6
   6   2  10   7   5   3   4   8   9   1
   1   4   3   2  10   6   5   7   8   9
   5   7   1   9   6   4   8   2  10   3
   4  10   5   6   3   8   7   1   9   2

AppleScript

At its simplest, an AppleScript handler for the shuffle could be:

on sattoloShuffle(theList) -- In-place shuffle.
    repeat with i from (count theList) to 2 by -1
        set j to (random number from 1 to (i - 1))
        tell theList to set {item i, item j} to {item j, item i}
    end repeat
    return -- Return nothing (ie. not the result of the last action above).
end sattoloShuffle

But swapping values by list is inefficient in a repeat. Also, if an AppleScript list is quite to very long, access to its items is very much faster if the list variable is referred to as a property belonging to something rather than simply as a variable. In addition to this, using the language's built-in some specifier to select an item at random from a list is so much faster than sending an Apple event to invoke the StandardAdditions' random number command that, for the current purpose, it can be over 100 times as fast to set up an index list of the same length and select indices at random from that!

on sattoloShuffle(theList) -- In-place shuffle.
    -- Script object to which list variables can "belong".
    script o
        property lst : theList as list -- Original list.
        property indices : my lst's items -- Shallow copy.
    end script
    
    -- Populate the copy with indices. (No need to bother with the first.)
    set listLength to (count o's lst)
    repeat with i from 2 to listLength
        set item i of o's indices to i
    end repeat
    -- Repeatedly lose the first item in the index list and select an index at random from what's left.
    repeat with i from 1 to listLength - 1
        set o's indices to rest of o's indices
        set j to some item of o's indices
        set temp to item i of o's lst
        set item i of o's lst to item j of o's lst
        set item j of o's lst to temp
    end repeat
    return -- Return nothing (ie. not the result of the last action above).
end sattoloShuffle

-- Task demo:
local output, astid, aList
set output to {}
set astid to AppleScript's text item delimiters
set AppleScript's text item delimiters to ", "
repeat with aList in {{}, {10}, {10, 20}, {10, 20, 30}, {11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22}}
    set end of output to "Before: {" & aList & "}"
    sattoloShuffle(aList)
    set end of output to "After:  {" & aList & "}"
end repeat
set AppleScript's text item delimiters to linefeed
set output to output as text
set AppleScript's text item delimiters to astid
return output

Output:

Before: {}
After:  {}
Before: {10}
After:  {10}
Before: {10, 20}
After:  {20, 10}
Before: {10, 20, 30}
After:  {20, 30, 10}
Before: {11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22}
After:  {21, 22, 15, 11, 17, 12, 19, 16, 18, 14, 13, 20}

ARM Assembly

Works with: as version Raspberry Pi

/* ARM assembly Raspberry PI  */
/*  program sattolo.s   */

/************************************/
/* Constantes                       */
/************************************/
.equ STDOUT, 1     @ Linux output console
.equ EXIT,   1     @ Linux syscall
.equ WRITE,  4     @ Linux syscall
/*********************************/
/* Initialized data              */
/*********************************/
.data
sMessResult:      .ascii "Value  : "
sMessValeur:       .fill 11, 1, ' '            @ size => 11
szCarriageReturn: .asciz "\n"

.align 4
iGraine:  .int 123456
.equ NBELEMENTS,      9
TableNumber:	     .int   4,6,7,10,11,15,22,30,35

/*********************************/
/* UnInitialized data            */
/*********************************/
.bss  
/*********************************/
/*  code section                 */
/*********************************/
.text
.global main 
main:                                           @ entry of program 
    ldr r0,iAdrTableNumber                      @ address number table
    mov r1,#NBELEMENTS                          @ number of élements 
    bl satShuffle
    ldr r2,iAdrTableNumber
    mov r3,#0
1:                                              @ loop display table
	ldr r0,[r2,r3,lsl #2]
    ldr r1,iAdrsMessValeur                      @ display value
    bl conversion10                             @ call function
    ldr r0,iAdrsMessResult
    bl affichageMess                            @ display message
    add r3,#1
    cmp r3,#NBELEMENTS - 1
    ble 1b

    ldr r0,iAdrszCarriageReturn
    bl affichageMess   
    /*    2e shuffle             */
    ldr r0,iAdrTableNumber                     @ address number table
    mov r1,#NBELEMENTS                         @ number of élements 
    bl satShuffle
    ldr r2,iAdrTableNumber
    mov r3,#0
2:                                             @ loop display table
    ldr r0,[r2,r3,lsl #2]
    ldr r1,iAdrsMessValeur                     @ display value
    bl conversion10                            @ call function
    ldr r0,iAdrsMessResult
    bl affichageMess                           @ display message
    add r3,#1
    cmp r3,#NBELEMENTS - 1
    ble 2b

100:                                           @ standard end of the program 
    mov r0, #0                                 @ return code
    mov r7, #EXIT                              @ request to exit program
    svc #0                                     @ perform the system call

iAdrsMessValeur:          .int sMessValeur
iAdrszCarriageReturn:     .int szCarriageReturn
iAdrsMessResult:          .int sMessResult
iAdrTableNumber:          .int TableNumber

/******************************************************************/
/*     Sattolo Shuffle                                  */ 
/******************************************************************/
/* r0 contains the address of table */
/* r1 contains the number of elements */
satShuffle:
    push {r2-r6,lr}                                    @ save registers
    mov r5,r0                                          @ save table address
    mov r2,#1                                          @ start index
    mov r4,r1                                          @ last index + 1
1:
    sub r1,r2,#1                                       @ index - 1
    mov r0,r1                                          @ generate aleas
    bl genereraleas
    ldr r3,[r5,r1,lsl #2]                              @ swap number on the table
    ldr r6,[r5,r0,lsl #2]
    str r6,[r5,r1,lsl #2]
    str r3,[r5,r0,lsl #2]
    add r2,#1                                           @ next number
    cmp r2,r4                                           @ end ?
    ble 1b                                              @ no -> loop

100:
    pop {r2-r6,lr}
    bx lr                                               @ return 

/******************************************************************/
/*     display text with size calculation                         */ 
/******************************************************************/
/* r0 contains the address of the message */
affichageMess:
    push {r0,r1,r2,r7,lr}                          @ save  registres
    mov r2,#0                                      @ counter length 
1:                                                 @ loop length calculation 
    ldrb r1,[r0,r2]                                @ read octet start position + index 
    cmp r1,#0                                      @ if 0 its over 
    addne r2,r2,#1                                 @ else add 1 in the length 
    bne 1b                                         @ and loop 
                                                   @ so here r2 contains the length of the message 
    mov r1,r0                                      @ address message in r1 
    mov r0,#STDOUT                                 @ code to write to the standard output Linux 
    mov r7, #WRITE                                 @ code call system "write" 
    svc #0                                         @ call systeme 
    pop {r0,r1,r2,r7,lr}                           @ restaur des  2 registres */ 
    bx lr                                          @ return  
/******************************************************************/
/*     Converting a register to a decimal unsigned                */ 
/******************************************************************/
/* r0 contains value and r1 address area   */
/* r0 return size of result (no zero final in area) */
/* area size => 11 bytes          */
.equ LGZONECAL,   10
conversion10:
    push {r1-r4,lr}                                 @ save registers 
    mov r3,r1
    mov r2,#LGZONECAL

1:	                                            @ start loop
    bl divisionpar10U                               @unsigned  r0 <- dividende. quotient ->r0 reste -> r1
    add r1,#48                                      @ digit
    strb r1,[r3,r2]                                 @ store digit on area
    cmp r0,#0                                       @ stop if quotient = 0 
    subne r2,#1                                     @ else previous position
    bne 1b	                                    @ and loop
                                                    @ and move digit from left of area
    mov r4,#0
2:
    ldrb r1,[r3,r2]
    strb r1,[r3,r4]
    add r2,#1
    add r4,#1
    cmp r2,#LGZONECAL
    ble 2b
                                                    @ and move spaces in end on area
    mov r0,r4                                       @ result length 
    mov r1,#' '                                     @ space
3:
    strb r1,[r3,r4]                                 @ store space in area
    add r4,#1                                       @ next position
    cmp r4,#LGZONECAL
    ble 3b                                          @ loop if r4 <= area size

100:
    pop {r1-r4,lr}                                  @ restaur registres 
    bx lr                                           @return

/***************************************************/
/*   division par 10   unsigned                    */
/***************************************************/
/* r0 dividende   */
/* r0 quotient */	
/* r1 remainder  */
divisionpar10U:
    push {r2,r3,r4, lr}
    mov r4,r0                                       @ save value
    //mov r3,#0xCCCD                                @ r3 <- magic_number lower  raspberry 3
    //movt r3,#0xCCCC                               @ r3 <- magic_number higter raspberry 3
    ldr r3,iMagicNumber                             @ r3 <- magic_number    raspberry 1 2
    umull r1, r2, r3, r0                            @ r1<- Lower32Bits(r1*r0) r2<- Upper32Bits(r1*r0) 
    mov r0, r2, LSR #3                              @ r2 <- r2 >> shift 3
    add r2,r0,r0, lsl #2                            @ r2 <- r0 * 5 
    sub r1,r4,r2, lsl #1                            @ r1 <- r4 - (r2 * 2)  = r4 - (r0 * 10)
    pop {r2,r3,r4,lr}
    bx lr                                           @ leave function 
iMagicNumber:  	.int 0xCCCCCCCD
/***************************************************/
/*   Generation random number                  */
/***************************************************/
/* r0 contains limit  */
genereraleas:
    push {r1-r4,lr}                                  @ save registers 
    ldr r4,iAdriGraine
    ldr r2,[r4]
    ldr r3,iNbDep1
    mul r2,r3,r2
    ldr r3,iNbDep1
    add r2,r2,r3
    str r2,[r4]                                      @ maj de la graine pour l appel suivant 
    cmp r0,#0
    beq 100f
    mov r1,r0                                        @ divisor
    mov r0,r2                                        @ dividende
    bl division
    mov r0,r3                                        @ résult = remainder
  
100:                                                 @ end function
    pop {r1-r4,lr}                                   @ restaur registers
    bx lr                                            @ return
/*****************************************************/
iAdriGraine: .int iGraine	
iNbDep1: .int 0x343FD
iNbDep2: .int 0x269EC3 
/***************************************************/
/* integer division unsigned                       */
/***************************************************/
division:
    /* r0 contains dividend */
    /* r1 contains divisor */
    /* r2 returns quotient */
    /* r3 returns remainder */
    push {r4, lr}
    mov r2, #0                                         @ init quotient
    mov r3, #0                                         @ init remainder
    mov r4, #32                                        @ init counter bits
    b 2f
1:                                                     @ loop 
    movs r0, r0, LSL #1                                @ r0 <- r0 << 1 updating cpsr (sets C if 31st bit of r0 was 1)
    adc r3, r3, r3                                     @ r3 <- r3 + r3 + C. This is equivalent to r3 ? (r3 << 1) + C 
    cmp r3, r1                                         @ compute r3 - r1 and update cpsr 
    subhs r3, r3, r1                                   @ if r3 >= r1 (C=1) then r3 <- r3 - r1 
    adc r2, r2, r2                                     @ r2 <- r2 + r2 + C. This is equivalent to r2 <- (r2 << 1) + C 
2:
    subs r4, r4, #1                                    @ r4 <- r4 - 1 
    bpl 1b                                             @ if r4 >= 0 (N=0) then loop
    pop {r4, lr}
    bx lr

Arturo

cycle: function [arr][
    if 2 > size arr -> return arr
    lastIndex: (size arr)-1
    result: new arr
    loop lastIndex..1 'i [
        j: random 0 i-1

        tmp: result\[i]
        set result i result\[j]
        set result j tmp
    ]
    return result
]

lists: [
    []
    [10]
    [10 20]
    [10 20 30]
    [11 12 13 14 15 16 17 18 19 20 21 22]
]

loop lists 'l ->
    print [l "->" cycle l]

Output:

[] -> [] 
[10] -> [10] 
[10 20] -> [20 10] 
[10 20 30] -> [20 30 10] 
[11 12 13 14 15 16 17 18 19 20 21 22] -> [14 11 18 17 12 20 16 19 21 22 15 13]

AutoHotkey

loop 3
{
    testCases:= [[]
                ,[10]
                ,[10, 20]
                ,[10, 20, 30]
                ,[11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22]]

    for n, items in testCases
    {
        Sattolo_cycle(items)
        res := "["
        for m, v in items
            res .= v ", "
        result .= Trim(res, ", ") "]`n"
    }
    result .= "`n"
}
MsgBox % result
return

Sattolo_cycle(ByRef items){
    i := items.Count()
    while (i>1)
    {
        Random, j, 1, i-1
        t := items[i], items[i] := items[j], items[j] := t
        i--
    }
}

Output:

[]
[10]
[20, 10]
[20, 30, 10]
[21, 15, 22, 17, 11, 12, 13, 14, 16, 18, 20, 19]

[]
[10]
[20, 10]
[20, 30, 10]
[18, 13, 20, 17, 19, 15, 21, 16, 14, 22, 12, 11]

[]
[10]
[20, 10]
[30, 10, 20]
[21, 17, 14, 12, 13, 11, 16, 22, 15, 18, 20, 19]

BaCon

OPTION BASE 1

SUB Swap_Array(array[], total)

    FOR i = total DOWNTO 1
        j = RANDOM(i-1)+1
        SWAP array[i], array[j]
    NEXT
    PRINT COIL$(total, STR$(array[_]))

ENDSUB

DECLARE demo1[] = { }
Swap_Array(demo1, UBOUND(demo1))

DECLARE demo2[] = { 10 }
Swap_Array(demo2, UBOUND(demo2))

DECLARE demo3[] = { 10, 20 }
Swap_Array(demo3, UBOUND(demo3))

DECLARE demo4[] = { 10, 20, 30 }
Swap_Array(demo4, UBOUND(demo4))

DECLARE demo5[] = { 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 }
Swap_Array(demo5, UBOUND(demo5))

Output:

...<empty line>...
10
20 10
20 30 10
16 19 15 21 14 22 11 20 13 17 18 12

BQN

Uses a fold in order to make the swaps in a functional style. It doesn't mutate the argument array, but after the initial copy is made CBQN is able to update it in place.

Sattolo ← {
  Swap ← {
    i 𝕊 𝕩:
    j ← •rand.Range i
    ⌽⌾(i‿j⊸⊏) 𝕩
  }
  𝕩 Swap´ 1↓↕≠𝕩
}

>(⋈Sattolo)¨⟨
  ⟨⟩
  ⟨10⟩
  ⟨10, 20⟩
  ⟨10, 20, 30⟩
  ⟨11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22⟩
⟩

Possible Output:

┌─                                         
╵ ⟨⟩                                       
  ⟨ 10 ⟩                                   
  ⟨ 20 10 ⟩                                
  ⟨ 20 30 10 ⟩                             
  ⟨ 17 20 15 22 19 21 16 14 18 13 12 11 ⟩  
                                          ┘

C

This is generic to the extreme, although the function is technically being fed strings, it can handle any type, as shown in the outputs below :

Interactive and without hardcoded inputs

#include<stdlib.h>
#include<stdio.h>
#include<time.h>

void sattoloCycle(void** arr,int count){
	int i,j;
	void* temp;
	
	if(count<2)
		return;
	for(i=count-1;i>=1;i--){
		j = rand()%i;
		temp = arr[j];
		arr[j] = arr[i];
		arr[i] = temp;
	}
}

int main(int argC,char* argV[])
{
	int i;
	
	if(argC==1)
		printf("Usage : %s <array elements separated by a space each>",argV[0]);
	else{
                srand((unsigned)time(NULL));
		sattoloCycle((void*)(argV + 1),argC-1);
		
		for(i=1;i<argC;i++)
			printf("%s ",argV[i]);
	}
	return 0;
}

Output:

C:\rosettaCode>sattoloCycle.exe ""

C:\rosettaCode>sattoloCycle.exe 10
10
C:\rosettaCode>sattoloCycle.exe 10 20
20 10
C:\rosettaCode>sattoloCycle.exe 10 20 30
30 10 20
C:\rosettaCode>sattoloCycle.exe 11 12 13 14 15 16 17 18 19 20 21 22
16 17 11 12 13 20 22 14 15 21 18 19
C:\rosettaCode>sattoloCycle.exe s a t t o l o C y c l e
l o s a t c e t o l C y
C:\rosettaCode>sattoloCycle.exe 1 2.3 4.2 1 3 e r q t 2 1 oo 2.1 eds
1 2.1 2.3 q r eds 1 e 3 t 1 2 oo 4.2
C:\rosettaCode>sattoloCycle.exe totally mixed up random string ( 1 2.3 2 ) which will get even more { a 2 q.1 } mixed up.
mixed q.1 a 1 up ) 2 even { will ( } 2 more totally random get which string up. 2.3 mixed

Non Interactive and with hardcoded inputs

Same code but with hardcoded integer arrays as in the task to show that the function can handle any type.

#include<stdlib.h>
#include<stdio.h>
#include<time.h>

void sattoloCycle(void** arr,int count){
	int i,j;
	void* temp;
	
	if(count<2)
		return;
	for(i=count-1;i>=1;i--){
		j = rand()%i;
		temp = arr[j];
		arr[j] = arr[i];
		arr[i] = temp;
	}
}

int main()
{
	int i;
	
	int a[] = {};
	int b[] = {10};
	int c[] = {10, 20};
	int d[] = {10, 20, 30};
	int e[] = {11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22};

	srand((unsigned)time(NULL));
	sattoloCycle((void*)a,0);
		
	printf("\nShuffled a = ");
	for(i=0;i<0;i++)
		printf("%d ",a[i]);
		
	sattoloCycle((void*)b,1);
		
	printf("\nShuffled b = ");
	for(i=0;i<1;i++)
		printf("%d ",b[i]);
			
	sattoloCycle((void*)c,2);
		
	printf("\nShuffled c = ");
	for(i=0;i<2;i++)
		printf("%d ",c[i]);
	
	sattoloCycle((void*)d,3);
		
	printf("\nShuffled d = ");
	for(i=0;i<3;i++)
		printf("%d ",d[i]);
		
	sattoloCycle((void*)e,12);
		
	printf("\nShuffled e = ");
	for(i=0;i<12;i++)
		printf("%d ",e[i]);

	return 0;
}

Output:

Shuffled a =
Shuffled b = 10
Shuffled c = 20 10
Shuffled d = 20 30 10
Shuffled e = 13 18 14 20 17 15 21 19 16 12 22 11

C#

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;
    }
}

C++

#include <ctime>
#include <string>
#include <iostream>
#include <algorithm>

class cycle{
public:
    template <class T>
    void cy( T* a, int len ) {
        int i, j;
        show( "original: ", a, len );
        std::srand( unsigned( time( 0 ) ) );

        for( int i = len - 1; i > 0; i-- ) {
            do {
                j = std::rand() % i;
            } while( j >= i );
            std::swap( a[i], a[j] );
        }

        show( "  cycled: ", a, len ); std::cout << "\n";
    }
private:
    template <class T>
    void show( std::string s, T* a, int len ) {
        std::cout << s;
        for( int i = 0; i < len; i++ ) {
            std::cout << a[i] << " ";
        }
        std::cout << "\n";
    }
};
int main( int argc, char* argv[] ) {
    std::string d0[] = { "" },
                d1[] = { "10" },
                d2[] = { "10", "20" };
    int         d3[] = { 10, 20, 30 },
                d4[] = { 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 };
    cycle c;
    c.cy( d0, sizeof( d0 ) / sizeof( d0[0] ) );
    c.cy( d1, sizeof( d1 ) / sizeof( d1[0] ) );
    c.cy( d2, sizeof( d2 ) / sizeof( d2[0] ) );
    c.cy( d3, sizeof( d3 ) / sizeof( d3[0] ) );
    c.cy( d4, sizeof( d4 ) / sizeof( d4[0] ) );

    return 0;
}

Output:

original:
  cycled:

original: 10
  cycled: 10

original: 10 20
  cycled: 20 10

original: 10 20 30
  cycled: 30 10 20

original: 11 12 13 14 15 16 17 18 19 20 21 22
  cycled: 13 17 14 22 11 18 20 12 21 19 15 16

D

import std.stdio;

void main() {
    auto items = [0,1,2,3,4,5];
    sattoloCycle(items);
    items.writeln;
}

/// The Sattolo cycle is an algorithm for randomly shuffling an array in such a way that each element ends up in a new position.
void sattoloCycle(R)(R items) {
    import std.algorithm : swapAt;
    import std.random : uniform;

    for (int i=items.length; i-- > 1;) {
        int j = uniform(0, i);
        items.swapAt(i, j);
    }
}

unittest {
    import std.range : lockstep;
    auto o = ['a', 'b', 'c', 'd', 'e'];

    auto s = o.dup;
    sattoloCycle(s);
    foreach (a, b; lockstep(o, s)) {
        assert(a != b, "An element stayed in place unexpectedly.");
    }
}

Output:

Several runs shown

[2, 4, 1, 5, 3, 0]
[3, 0, 4, 5, 1, 2]
[3, 5, 4, 1, 0, 2]
[5, 4, 3, 0, 2, 1]

Delphi

Works with: Delphi version 6.0

Library: SysUtils,StdCtrls

procedure DoSattoloCycle(var IA: array of integer);
{Shuffle integers in array using Sattolo cycle}
var I,J,T: integer;
begin
{Make sure random number generator is random}
Randomize;
{Randomly shuffle every item in the array}
for I:=High(IA) downto 0 do
	begin
	J:=Random(I);
	T:=IA[I]; IA[I]:=IA[J]; IA[J]:=T;
	end;
end;

{Test data specified in problem}

var SatTest1: array of integer;
var SatTest2: array [0..0] of integer = (10);
var SatTest3: array [0..1] of integer = (10, 20);
var SatTest4: array [0..2] of integer = (10, 20, 30);
var SatTest5: array [0..11] of integer = (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22);


procedure ShowSattoloCycle(Memo: TMemo);

	procedure ShowIntArray(Title: string; IA: array of integer);
	{Display title and array}
	var I: integer;
	var S: string;
	begin
	S:=Title+' [';
	for I:=0 to High(IA) do
		begin
		if I<>0 then S:=S+' ';
		S:=S+IntToStr(IA[I]);
		end;
	S:=S+']';
	Memo.Lines.Add(S);
	end;


	procedure ShowShuffleData(var IA: array of integer);
	{Shuffle and display specified array}
	begin
	ShowIntArray('Original data:', IA);
	DoSattoloCycle(IA);
	ShowIntArray('Shuffled data:',IA);
	end;


begin
{Shuffle and display all data items}
ShowShuffleData(SatTest1);
ShowShuffleData(SatTest2);
ShowShuffleData(SatTest3);
ShowShuffleData(SatTest4);
ShowShuffleData(SatTest5);
end;

Output:

Original data: []
Shuffled data: []
Original data: [10]
Shuffled data: [10]
Original data: [10 20]
Shuffled data: [20 10]
Original data: [10 20 30]
Shuffled data: [20 30 10]
Original data: [11 12 13 14 15 16 17 18 19 20 21 22]
Shuffled data: [18 11 16 15 22 17 20 21 12 19 14 13]
Elapsed Time: 11.480 ms.

EasyLang

proc sattolo_cycle . a[] .
   for i = len a[] downto 2
      r = randint (i - 1)
      swap a[r] a[i]
   .
.
arr[] = [ 1 2 3 ]
sattolo_cycle arr[]
print arr[]

F#

let rnd=System.Random()
let sottolo(n:int[])=let rec fN g=match g with -1|0->() |_->let e=rnd.Next(g-1) in let l=n.[g] in n.[g]<-n.[e]; n.[e]<-l; fN (g-1) in fN((Array.length n)-1)
[[||];[|10|];[|10;20|];[|10;20;30|];[|11..22|]]|>List.iter(fun n->printf "%A->" n; sottolo n; printfn "%A" n)

Output:

[||]->[||]
[|10|]->[|10|]
[|10; 20|]->[|20; 10|]
[|10; 20; 30|]->[|20; 30; 10|]
[|11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22|]->[|17; 20; 16; 15; 18; 11; 14; 21; 12; 13; 22; 19|]

Factor

USING: arrays io kernel literals math math.ranges prettyprint
random sequences ;
IN: rosetta-code.sattolo-cycle

: (sattolo) ( seq -- seq' )
    dup dup length 1 - 1 [a,b]
    [ dup iota random rot exchange ] with each ;
    
: sattolo ( seq -- seq/seq' )
    dup length 1 > [ (sattolo) ] when ;

{
    { }
    { 10 }
    { 10 20 }
    { 10 20 30 }
    $[ 11 22 [a,b] >array ]
}
[
    [ "original: " write .         ]
    [ "cycled:   " write sattolo . ] bi nl
] each

Output:

original: { }
cycled:   { }

original: { 10 }
cycled:   { 10 }

original: { 10 20 }
cycled:   { 20 10 }

original: { 10 20 30 }
cycled:   { 30 10 20 }

original: { 11 12 13 14 15 16 17 18 19 20 21 22 }
cycled:   { 16 19 20 13 17 18 22 14 21 15 11 12 }

Free Pascal

program sattolocycle;
{$ifdef fpc}{$mode delphi}{$endif}
uses math;
var
  a:Array of cardinal = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19];
  i,j:integer;
  t:cardinal;
begin
  randomize;
  i := length(a);
  while i > 1 do  // do not touch this again!!!
  begin
    dec(i);
    j :=randomrange(0,i); 
    t:=a[i];a[i]:=a[j];a[j]:=t;
    write(a[i]:4);
  end;
  writeln;
end.

Example output in Free Pascal:
  2  14  12  13   0   1  15   9   7   6   3  18  10   4  16   5  19   8  11  17

FreeBASIC

' version 22-10-2016
' compile with: fbc -s console
' for boundry checks on array's compile with: fbc -s console -exx

' sort from lower bound to the highter bound
' array's can have subscript range from -2147483648 to +2147483647

Sub sattolo_cycle(a() As Long)

    Dim As Long lb = LBound(a)
    Dim As ULong n = UBound(a) - lb +1
    Dim As ULong i, j

    Randomize Timer

    For i = n -1 To 1 Step -1
        j =Fix(Rnd * (i))       ' 0 <= j < i
        Swap a(lb + i), a(lb + j)
    Next

End Sub

' ------=< MAIN >=------

Dim As Long i, array(1 To 52)

For i = 1 To 52 : array(i) = i : Next

Print "Starting array from 1 to 52"
For i = 1 To 52
    Print Using " ###";array(i);
Next : Print : Print

sattolo_cycle(array())

Print "After Sattolo_Cycle"
For i = 1 To 52
    Print Using " ###";array(i);
Next : Print : Print


' empty keyboard buffer 
While InKey <> "" : Wend
Print : Print "hit any key to end program"
Sleep
End

Output:

Starting array from 1 to 52
   1   2   3   4   5   6   7   8   9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52

After Sattolo_Cycle
  40  48   7  25  32  17  44   4   8  13  18  47   5  29  10  20  49  39  11  51   3  21  46   2  38  16  28  37  12  50   1   9  52  19  22  30  36  27  45  15  24  23  33  41  14  31  43  26  35  34  42   6

FutureBasic

include "NSLog.incl"

void local fn SattoloCycle( mutArr as CFMutableArrayRef )
  NSUInteger i, j, count = len(mutArr)
  
  for i = 0 to count - 1
    cln j = arc4random_uniform( i );
    MutableArrayExchangeObjects( mutArr, i, j )
  next
end fn

NSUInteger i, count
CFMutableArrayRef mutArr
mutArr = fn MutableArrayWithArray( @[@"Alpha",@"Bravo",@"Charlie",@"Delta",@"Echo",@"Foxtrot"] )

for i = 0 to 5
  fn SattoloCycle( mutArr )
   NSLog( @"%@", mutArr )
next

HandleEvents

Output:

(
    Charlie,
    Foxtrot,
    Delta,
    Bravo,
    Alpha,
    Echo
)
(
    Echo,
    Alpha,
    Charlie,
    Foxtrot,
    Delta,
    Bravo
)
(
    Charlie,
    Delta,
    Foxtrot,
    Bravo,
    Echo,
    Alpha
)
(
    Delta,
    Bravo,
    Echo,
    Alpha,
    Charlie,
    Foxtrot
)
(
    Alpha,
    Delta,
    Foxtrot,
    Echo,
    Bravo,
    Charlie
)
(
    Echo,
    Charlie,
    Alpha,
    Bravo,
    Delta,
    Foxtrot
)

Go

package main

import (
	"math/rand"
	"fmt"
)

func main() {
	list := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
	for i := 1; i <= 10; i++ {
		sattoloCycle(list)
		fmt.Println(list)
	}
}

func sattoloCycle(list []int) {
	for x := len(list) -1; x > 0; x-- {
		j := rand.Intn(x)
		list[x], list[j] = list[j], list[x]
	}
}

Output:

[4 5 1 7 3 9 10 2 8 6]
[7 9 5 1 2 3 4 8 6 10]
[2 3 9 4 6 8 7 1 10 5]
[6 2 10 1 8 4 5 9 7 3]
[8 3 7 2 10 1 6 4 9 5]
[7 5 1 4 9 2 3 10 6 8]
[6 8 3 10 2 4 7 1 5 9]
[1 6 8 7 9 5 4 2 3 10]
[9 5 10 6 2 8 1 7 4 3]
[7 3 1 10 4 2 8 6 5 9]

Haskell

import Control.Monad ((>=>), (>>=), forM_)
import Control.Monad.Primitive
import qualified Data.Vector as V
import qualified Data.Vector.Mutable as M
import System.Random.MWC

type MutVec m a = M.MVector (PrimState m) a

-- Perform an in-place shuffle of the vector, making it a single random cyclic
-- permutation of its initial value.  The vector is also returned for
-- convenience.
cyclicPermM :: PrimMonad m => Gen (PrimState m) -> MutVec m a -> m (MutVec m a)
cyclicPermM rand vec = forM_ [1..M.length vec-1] upd >> return vec
  where upd i = uniformR (0, i-1) rand >>= M.swap vec i

-- Return a vector that is a single random cyclic permutation of the argument.
cyclicPerm :: PrimMonad m => Gen (PrimState m) -> V.Vector a -> m (V.Vector a)
cyclicPerm rand = V.thaw >=> cyclicPermM rand >=> V.unsafeFreeze

--------------------------------------------------------------------------------

test :: Show a => [a] -> IO ()
test xs = do
  let orig = V.fromList xs
  cyc <- withSystemRandom . asGenIO $ \rand -> cyclicPerm rand orig
  putStrLn $ "original: " ++ show orig
  putStrLn $ "  cycled: " ++ show cyc

main :: IO ()
main = do
  test ([] :: [()])
  test [10 :: Int]
  test [10, 20 :: Int]
  test [10, 20, 30 :: Int]
  test [11..22 :: Int]
  -- Also works for other types.
  test "abcdef"

Output:

$ ./sattolo 
original: []
  cycled: []
original: [10]
  cycled: [10]
original: [10,20]
  cycled: [20,10]
original: [10,20,30]
  cycled: [20,30,10]
original: [11,12,13,14,15,16,17,18,19,20,21,22]
  cycled: [13,14,16,11,17,20,18,21,22,15,19,12]
original: "abcdef"
  cycled: "cfeabd"

J

The key "feature" of this algorithm is that it cannot generate some legal random permutations. For example, given a two element list, it will always reverse that list.

Implementation:

sattolo=:3 :0
  for_i.}:i.-#y do.
    j=.?i
    y=. (<i,j) C. y
  end.
  y
)

Example use:

   sattolo ''

   sattolo ,10
10
   sattolo 10 20
20 10
   sattolo 10 20 30
30 10 20
   sattolo 11+i.12
19 18 15 21 12 17 22 16 20 13 11 14

Java

private static final Random rng = new Random();

void sattoloCycle(Object[] items) {
    for (int i = items.length-1; i > 0; i--) {
        int j = rng.nextInt(i);
        Object tmp = items[i];
        items[i] = items[j];
        items[j] = tmp;
    }
}

JavaScript

function sattoloCycle(items) {
    for (var i = items.length-1; i > 0; i--) {
        var j = Math.floor(Math.random() * i);
        var tmp = items[i];
        items[i] = items[j];
        items[j] = tmp;
    }
}

Jsish

/* Sattolo cycle array shuffle, in Jsish */
function sattoloCycle(items:array):void {
    for (var i = items.length-1; i > 0; i--) {
        var j = Math.floor(Math.random() * i);
        var tmp = items[i];
        items[i] = items[j];
        items[j] = tmp;
    }
}

if (Interp.conf('unitTest')) {
    Math.srand(0);
    for (var a of [[], [10], [10,20], [10,20,30], [11,12,13,14,15,16,17,18,19,20,21,22]]) {
;       a;
        sattoloCycle(a);
;       a;
    }
}

/*
=!EXPECTSTART!=
a ==> []
a ==> []
a ==> [ 10 ]
a ==> [ 10 ]
a ==> [ 10, 20 ]
a ==> [ 20, 10 ]
a ==> [ 10, 20, 30 ]
a ==> [ 30, 10, 20 ]
a ==> [ 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 ]
a ==> [ 22, 11, 17, 15, 12, 14, 19, 13, 21, 18, 16, 20 ]
=!EXPECTEND!=
*/

Output:

prompt$ jsish -u sattoloCycle.jsi
[PASS] sattoloCycle.jsi

jq

Works with: jq

Works with gojq, the Go implementation of jq

Neither the C nor the Go implementations of jq has a built-in PRNG, but both are designed with the Unix toolset philosophy in mind, so in this entry we will use an external source of randomness rather than one of the PRNGs defined in jq as at RC.

Specifically, we will use /dev/urandom like so:

< /dev/urandom tr -cd '0-9' | fold -w 1 | jq -RMnrc -f program.jq

where program.jq is the following program:

# Output: a stream of prn in range(0;$n) where $n is . and $n > 1
def prns:
  . as $n
  | (($n-1)|tostring|length) as $w
  # Output: a prn in range(0;$n) 
  | def prn:
      [limit($w; inputs)] | join("") | tonumber
      | if . < $n then . else prn end;
  repeat(prn);

# Output: a prn in range(0;$n) where $n is .,
# b
def prn:
  if . == 1 then 0
  else . as $n
  | (($n-1)|tostring|length) as $w
  | [limit($w; inputs)] | join("") | tonumber
  | if . < $n then . else ($n | prn) end
  end;

def sattoloCycle:
  length as $n
  | if $n ==0 then [] 
    elif $n == 1 then empty   # a Sattolo cycle is not possible
    else {i: $n, a: .}
    | until(.i ==  1;         # n.b.
        .i += -1
        | (.i | prn) as $j    # this line distinguishes the Sattolo cycle from the Knuth shuffle
        | .a[.i] as $t
        | .a[.i] = .a[$j]
        | .a[$j] = $t)
    | .a 
    end;

def task:
  [],
  [10,20],
  [10,20,30],
  [range(11;23)]
  | sattoloCycle;

task

Output:

[]
[20,10]
[20,30,10]
[17,13,14,15,20,21,19,16,18,22,12,11]

Julia

Works with: Julia version 0.6

function sattolocycle!(arr::Array, last::Int=length(arr))
    for i in last:-1:2
        j = rand(1:i-1)
        arr[i], arr[j] = arr[j], arr[i]
    end
    return arr
end

@show sattolocycle!([])
@show sattolocycle!([10])
@show sattolocycle!([10, 20, 30])
@show sattolocycle!([11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22])

Output:

sattolocycle!([]) = Any[]
sattolocycle!([10]) = [10]
sattolocycle!([10, 20, 30]) = [30, 10, 20]
sattolocycle!([11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22]) = [19, 20, 15, 11, 17, 18, 21, 22, 13, 16, 12, 14]

Kotlin

// version 1.0.6

fun <T> sattolo(items: Array<T>) {
    for (i in items.size - 1 downTo 1) {
        val j = (Math.random() * i).toInt()
        val t = items[i]
        items[i] = items[j]
        items[j] = t
    }
}

fun main(args: Array<String>) {
    val items = arrayOf(11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
    println(items.joinToString())
    sattolo(items)
    println(items.joinToString())
}

Sample output:

Output:

11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22
22, 11, 19, 12, 21, 14, 18, 20, 17, 16, 13, 15

Lua

function sattolo (items)
    local j
    for i = #items, 2, -1 do
        j = math.random(i - 1)
        items[i], items[j] = items[j], items[i]
    end
end

math.randomseed(os.time())
local testCases = {
    {},
    {10},
    {10, 20},
    {10, 20, 30},
    {11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22}
}
for _, array in pairs(testCases) do
    sattolo(array)
    print("[" .. table.concat(array, ", ") .. "]")
end

Output:

[]
[10]
[20, 10]
[30, 10, 20]
[15, 17, 22, 18, 16, 19, 21, 11, 12, 13, 20, 14]

Modula-2

MODULE SattoloCycle;
FROM FormatString IMPORT FormatString;
FROM RandomNumbers IMPORT Randomize,Random;
FROM Terminal IMPORT WriteString,WriteLn,ReadChar;

PROCEDURE SwapInt(VAR a,b : INTEGER);
VAR t : INTEGER;
BEGIN
    t := a;
    a := b;
    b := t;
END SwapInt;

TYPE
    ARR = ARRAY[0..5] OF INTEGER;
VAR
    buf : ARRAY[0..63] OF CHAR;
    items : ARR;
    i,j : INTEGER;
BEGIN
    Randomize(0);
    items := ARR{0,1,2,3,4,5};

    FOR i:=0 TO HIGH(items) DO
        j := Random(0,i);
        SwapInt(items[i], items[j]);
    END;

    FOR i:=0 TO HIGH(items) DO
        FormatString(" %i", buf, items[i]);
        WriteString(buf)
    END;

    ReadChar
END SattoloCycle.

Nim

Translation of: C

import random

proc sattoloCycle[T](a: var openArray[T]) =
  for i in countdown(a.high, 1):
    let j = rand(int.high) mod i
    swap a[j], a[i]

var a: seq[int] = @[]
var b: seq[int] = @[10]
var c: seq[int] = @[10, 20]
var d: seq[int] = @[10, 20, 30]
var e: seq[int] = @[11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22]

randomize()

a.sattoloCycle()
echo "Shuffled a = ", $a

b.sattoloCycle()
echo "\nShuffled b = ", $b

c.sattoloCycle()
echo "\nShuffled c = ", $c

d.sattoloCycle()
echo "\nShuffled d = ", $d

e.sattoloCycle()
echo "\nShuffled e = ", $e

Output:

Shuffled a = @[]

Shuffled b = @[10]

Shuffled c = @[20, 10]

Shuffled d = @[20, 30, 10]

Shuffled e = @[20, 21, 14, 17, 13, 18, 12, 22, 11, 15, 16, 19]

Objeck

Translation of: Objeck

class Sattolo {
  function : Main(args : String[]) ~ Nil {
    array := [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
    SattoloCycle(array);
    array->ToString()->PrintLine();
  }

  function : SattoloCycle(items : Int[]) ~ Nil {
    each(i : items) {
      j := (Float->Random() * 100.0)->As(Int) % items->Size();
      tmp := items[i];
      items[i] := items[j];
      items[j] := tmp;
    };
  }
}

Output:

[9,8,4,5,10,1,2,6,3,7]

Objective-C

#import <Foundation/Foundation.h>

@interface NSMutableArray (SattoloCycle)
- (void)sattoloCycle;
@end
@implementation NSMutableArray (SattoloCycle)
- (void)sattoloCycle {
  for (NSUInteger i = self.count-1; i > 0; i--) {
    NSUInteger j = arc4random_uniform(i);
    [self exchangeObjectAtIndex:i withObjectAtIndex:j];
  }
}
@end

OCaml

let sattolo_cycle arr =
  for i = Array.length arr - 1 downto 1 do
    let j = Random.int i in
    let temp = arr.(i) in
    arr.(i) <- arr.(j);
    arr.(j) <- temp
  done

Pascal

Pascal does not have a random function. The following program complies with the ISO standard 7185 (Standard “Unextended” Pascal, level 1) except the random function utilized has been supplied by the compiler vendor. Although random is not standardized, the GPC (GNU Pascal Compiler), FPC (FreePascal compiler) and many other compilers support this UCSD Pascal extension.

program sattoloCycle(output);

var
	i: integer;
	sample1: array[0..0] of integer;
	sample2: array[0..1] of integer;
	sample3: array[0..2] of integer;
	sample4: array[0..11] of integer;

procedure shuffle(var item: array[itemMinimum..itemMaximum: integer] of integer);
var
	i, randomIndex, temporaryValue: integer;
begin
	for i := itemMaximum downto succ(itemMinimum) do
	begin
		randomIndex := random(i - itemMinimum) + itemMinimum;
		temporaryValue := item[randomIndex];
		item[randomIndex] := item[i];
		item[i] := temporaryValue
	end
end;

procedure printArray(var item: array[itemMinimum..itemMaximum: integer] of integer);
var
	i: integer;
begin
	for i := itemMinimum to itemMaximum do
	begin
		write(item[i]:5)
	end;
	writeLn
end;

begin
	sample1[0] := 10;
	sample2[0] := 10; sample2[1] := 20;
	sample3[0] := 10; sample3[1] := 20; sample3[2] := 30;
	sample4[0] := 11; sample4[1] := 12; sample4[2] := 13; sample4[3] := 14;
	sample4[4] := 15; sample4[5] := 16; sample4[6] := 17; sample4[7] := 18;
	sample4[8] := 19; sample4[9] := 20; sample4[10] := 21; sample4[11] := 22;
	
	shuffle(sample1); printArray(sample1);
	shuffle(sample2); printArray(sample2);
	shuffle(sample3); printArray(sample3);
	shuffle(sample4); printArray(sample4);
end.

Output:

   10
   20   10
   20   30   10
   16   11   20   13   17   18   19   14   12   21   22   15

Perl

@a = 0..30;

printf "%2d ", $_ for @a; print "\n";
sattolo_cycle(\@a);
printf "%2d ", $_ for @a; print "\n";

sub sattolo_cycle {
    my($array) = @_;
    for $i (reverse 0 .. -1+@$array) {
        my $j = int rand $i;
        @$array[$j, $i] = @$array[$i, $j];
    }
}

Output:

 0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
18  5  9 25  3 23 12  2 26 21 16  4 11 15 20  1 27 10 29  7  6 28 24  8 13 17 19  0 14 30 22

Phix

sequence cards = tagset(52)
puts(1,"Before: ")      ?cards
for i=52 to 2 by -1 do
    integer r = rand(i-1)
    {cards[r],cards[i]} = {cards[i],cards[r]}
end for
puts(1,"After:  ")      ?cards
for i=1 to 52 do
    if cards[i]=i then ?9/0 end if
end for
if sort(cards)!=tagset(52) then ?9/0 end if
puts(1,"Sorted: ")      ?sort(cards)

Output:

Before: {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52}
After:  {51,47,8,9,20,5,43,21,12,2,7,19,4,32,10,23,30,29,31,38,13,44,41,26,42,15,34,46,27,33,40,18,24,17,28,48,3,45,11,22,39,1,35,49,36,14,6,25,50,16,52,37}
Sorted: {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52}

PHP

function sattoloCycle($items) {
   for ($i = 0; $i < count($items); $i++) {
        $j = floor((mt_rand() / mt_getrandmax()) * $i);
        $tmp = $items[$i];
        $items[$i] = $items[$j];
        $items[$j] = $tmp;
    } 
    return $items;
}

Picat

go =>
  Tests = [[],
           [10],
           [10, 20],
           [10, 20, 30],
           [11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22],
           "sattolo cycle"],
  foreach(L in Tests)
    println(original=L),
    sattolo_cycle(L),
    println(shuffled=L),
    nl
  end,
  nl,
  foreach(_ in 1..10)
    L = 1..10,
    sattolo_cycle(L),
    println(L)
  end.

sattolo_cycle(L) =>
  foreach(I in L.len..-1..2)
    swap(L,I,random(1,I-1))
  end.

swap(L,I,J)  =>
  T = L[I],
  L[I] := L[J],
  L[J] := T.

Output:

original = []
shuffled = []

original = [10]
shuffled = [10]

original = [10,20]
shuffled = [20,10]

original = [10,20,30]
shuffled = [20,30,10]

original = [11,12,13,14,15,16,17,18,19,20,21,22]
shuffled = [17,15,11,16,20,12,21,19,22,18,14,13]

original = sattolo cycle
shuffled = a cyotltecsol

[7,6,10,1,3,5,8,2,4,9]
[6,10,5,8,7,3,9,1,2,4]
[9,4,10,5,8,1,3,7,2,6]
[7,10,4,2,6,1,8,3,5,9]
[3,1,9,5,7,2,10,4,8,6]
[8,10,2,5,6,9,3,4,7,1]
[7,10,2,5,9,4,3,6,1,8]
[8,7,1,10,6,4,3,9,5,2]
[9,1,2,6,3,7,8,5,10,4]
[7,4,8,10,9,2,5,1,6,3]

PicoLisp

(seed (in "/dev/urandom" (rd 8)))

(de sattolo (Lst)
   (for (N (length Lst) (>= N 2) (dec N))
      (let I (rand 1 (dec N))
         (xchg (nth Lst N) (nth Lst I)) ) ) )

(let L (range 1 15)
   (println 'before L)
   (sattolo L)
   (println 'after L) )

Output:

before (1 2 3 4 5 6 7 8 9 10 11 12 13 14 15)
after (4 1 12 6 2 13 9 11 8 5 3 14 7 15 10)

Python

>>> from random import randrange
>>> def sattoloCycle(items):
	for i in range(len(items) - 1, 0, -1):
		j = randrange(i)  # 0 <= j <= i-1
		items[j], items[i] = items[i], items[j]

		
>>> # Tests
>>> for _ in range(10):
	lst = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
	sattoloCycle(lst)
	print(lst)

	
[5, 8, 1, 2, 6, 4, 3, 9, 10, 7]
[5, 9, 8, 10, 4, 3, 6, 2, 1, 7]
[10, 5, 8, 3, 9, 1, 4, 2, 6, 7]
[10, 5, 2, 6, 9, 7, 8, 3, 1, 4]
[7, 4, 8, 5, 10, 3, 2, 9, 1, 6]
[2, 3, 10, 9, 4, 5, 8, 1, 7, 6]
[5, 7, 4, 6, 2, 9, 3, 10, 8, 1]
[3, 10, 7, 2, 9, 5, 8, 4, 1, 6]
[2, 6, 5, 3, 9, 8, 10, 7, 1, 4]
[3, 6, 2, 5, 10, 4, 1, 9, 7, 8]
>>>

Quackery

See Knuth shuffle#Quackery for notes re. the "in-place-ness" of this code.

  [ temp put
    2dup swap
    temp share swap peek
    temp share rot peek
    dip 
      [ swap
        temp take 
        swap poke 
        temp put ]  
    swap 
    temp take 
    swap poke ]                 is [exch]  ( n n [ --> [ )

  [ dup size 1 - times
      [ i 1+ dup random
        rot [exch] ] ]         is sattolo (     [ --> [ )

Output:

Testing in the Quackery shell. (REPL)

/O> ' [ 10 11 12 13 14 15 16 17 18 19 ] 
... 10 times [ sattolo dup echo cr ]
... 
[ 15 17 10 11 13 14 19 18 16 12 ]
[ 19 10 15 16 14 17 11 12 18 13 ]
[ 12 13 14 11 10 18 19 15 16 17 ]
[ 18 19 15 16 17 13 10 12 14 11 ]
[ 15 11 16 12 19 17 18 13 10 14 ]
[ 11 13 15 17 14 10 12 19 16 18 ]
[ 10 17 12 18 11 13 14 16 15 19 ]
[ 19 18 16 15 17 12 13 10 14 11 ]
[ 16 19 15 12 18 10 14 11 17 13 ]
[ 14 17 16 11 10 15 13 18 12 19 ]

Stack: [ 14 17 16 11 10 15 13 18 12 19 ] 

/O> 10 times [ sattolo dup echo cr ]
... 
[ 11 13 10 16 18 19 14 12 15 17 ]
[ 17 11 19 13 10 15 18 16 12 14 ]
[ 18 13 15 17 16 12 14 19 11 10 ]
[ 10 19 12 18 13 11 16 17 14 15 ]
[ 15 10 14 16 18 13 12 19 17 11 ]
[ 10 14 12 17 19 18 13 16 11 15 ]
[ 15 19 13 12 17 10 11 14 18 16 ]
[ 17 11 12 15 18 13 10 16 14 19 ]
[ 12 10 18 14 11 16 13 19 17 15 ]
[ 14 16 17 18 12 11 19 15 13 10 ]

Stack: [ 14 16 17 18 12 11 19 15 13 10 ]

R

Basically identical to https://rosettacode.org/wiki/Knuth_shuffle#Short_version We've only changed an i to an i-1, changed the function names, and added the [11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22] test.

sattolo <- function(vec)
{
  last <- length(vec)
  if(last >= 2)
  {
    for(i in last:2)
    {
      j <- sample(seq_len(i - 1), size = 1)
      vec[c(i, j)] <- vec[c(j, i)]
    } 
  }
  vec
}
#Demonstration:
sattolo(integer(0))
sattolo(c(10))
replicate(10, sattolo(c(10, 20)))
replicate(10, sattolo(c(10, 20, 30)))
sattolo(c(11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22))
sattolo(c("Also", "works", "for", "strings"))

Output:

> sattolo(integer(0))
integer(0)
> sattolo(c(10))
[1] 10
> replicate(10, sattolo(c(10, 20)))
     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,]   20   20   20   20   20   20   20   20   20    20
[2,]   10   10   10   10   10   10   10   10   10    10
> replicate(10, sattolo(c(10, 20, 30)))
     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,]   30   30   20   20   30   20   20   20   20    20
[2,]   10   10   30   30   10   30   30   30   30    30
[3,]   20   20   10   10   20   10   10   10   10    10
> sattolo(c(11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22))
 [1] 12 13 15 16 20 11 22 17 14 21 18 19
> sattolo(c("Also", "works", "for", "strings"))
[1] "strings" "for"     "Also"    "works"

Racket

#lang racket

;; although the shuffle is in-place, returning the shuffled vector makes
;; testing a little easier
(define (sattolo-shuffle v)
  (for ((i (in-range (sub1 (vector-length v)) 0 -1)))
    (define j (random i))
    (define tmp (vector-ref v i))
    (vector-set! v i (vector-ref v j))
    (vector-set! v j tmp))
  v)

(define (derangement-of? A B #:strict? (strict? #t))
  (match* (A B)
    [('() '()) #t]
    [((list a) (list a)) #:when strict? #t]
    [((list a _ ...) (list a _ ...)) #f]
    [((list _ as ...) (list _ bs ...))
     (derangement-of? as bs #:strict? #t)]
    [((vector as ...) (vector bs ...))
     (derangement-of? as bs #:strict? strict?)]))

(module+ test
  (require rackunit)

  (check-equal? (sattolo-shuffle (vector)) #())
  (check-equal? (sattolo-shuffle (vector 10)) #(10))
  (check-equal? (sattolo-shuffle (vector 'inky)) #(inky))

  (define v′ (sattolo-shuffle (vector 11 12 13 14 15 16 17 18 19 20 21)))

  v′
  
  (check-true (derangement-of? #(11 12 13 14 15 16 17 18 19 20 21) v′)))

Output:

'#(21 19 12 11 18 17 14 16 15 13 20)

Raku

(formerly Perl 6)

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

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

my @a = flat 'A' .. 'Z', 'a' .. 'z';

say @a;
sattolo-cycle(@a);
say @a;

Sample output:

[A B C D E F G H I J K L M N O P Q R S T U V W X Y Z a b c d e f g h i j k l m n o p q r s t u v w x y z]
[r G w g W Z D X M f Q A c i H Y J F s z m v x P b U j n q I N e O L o C d u a K S V l y R T B k t h p E]

REXX

version 1

This REXX example uses a zero-based array; (to match the pseudo-code).

The array elements values can be of any type (even mixed): integer, floating point, characters, ···

The values of the array elements are specified via the command line (C.L.).

/*REXX program  implements and displays a  Sattolo shuffle  for an array  (of any type).*/
parse arg a;    say 'original:'      space(a)    /*obtain args from the CL; display 'em.*/
  do x=0  for words(a);  @.x= word(a, x+1);  end /*assign all elements to the @. array. */
                                                 /* [↑]  build an array of given items. */
       do #=x-1  by -1  to 1;  j= random(0, #-1) /*get a random integer between 0 & #-1.*/
       parse value @.#  @.j    with    @.j  @.#  /*swap two array elements, J is random.*/
       end   /*j*/                               /* [↑]  shuffle @ via Sattolo algorithm*/
$=                                               /* [↓]  build a list of shuffled items.*/
       do k=0  for x;   $= $  @.k;   end  /*k*/  /*append the next element in the array.*/
say  ' Sattolo:'        strip($)                 /*stick a fork in it,  we're all done. */

output when using the input of: [a null]

original: 
 Sattolo:

output when using the input of: 10

original: 10
 Sattolo: 10

output when using the input of: 10 20

original: 10 20 
 Sattolo: 20 10

output when using the input of: 10 20 30

original: 10 20 30
 Sattolo: 20 30 10

output when using the input of: 11 12 13 14 15 16 17 18 19 20 21 22

original: 11 12 13 14 15 16 17 18 19 20 21 22
 Sattolo: 15 14 17 19 18 12 22 13 20 21 11 16

output when using the input of: -1 0 00 oNe 2.7 /\ [] +6e1 ~~~

original: -1 0 00 one 2.7 /\ [] +6e1 ~~~
 Sattolo: /\ 00 +6e1 0 ~~~ oNe -1 2.7 []

version 2

/* REXX */
n=25
Do i=0 To n
  a.i=i
  b.i=i
  End
Call show ' pre'
Do i=n to 1 By -1
  j=random(0,i-1)
  Parse Value a.i a.j With a.j a.i
  End
Call show 'post'
Do i=0 To n
  If a.i=b.i Then
    Say i a.i '=' b.i
  End
Exit
Show:
ol=arg(1)
Do i=0 To n
  ol=ol right(a.i,2)
  End
Say ol
Return

Output:

 pre  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
post  3  4  8 18 14 21 20 13 10  1 25  7  2 24 12 23  5 11  6 22 16 19  9  0 15 17

Ring

# Project : Sattolo cycle

a = "123456789abcdefghijklmnopqrstuvwxyz"
n = len(a)
sit = list(n)    
 
for i = 1 to n			
    sit[i] = substr(a, i, 1)
next 
showsit()			
for i = n to 1 step -1
    j = floor(i * random(9)/10) + 1
    h = sit[i]
    sit[i] = sit[j]
    sit[j] = h
next  
showsit()
			
func showsit
     for i = 1 to n
         see sit[i] + " "
     next 
     see nl

Output:

1 2 3 4 5 6 7 8 9 a b c d e f g h i j k l m n o p q r s t u v w x y z 
i v 3 c 7 x 6 5 4 n a b r t e f g 2 8 u m o p w q l j h 9 s d y k z 1

RPL

Works with: Halcyon Calc version 4.2.7

RPL code

Comment

≪ 
  DUP SIZE 2 FOR j
      j 1 - RAND * FLOOR 1 +
      DUP2 GET 3 PICK j GET SWAP 4 ROLLD PUT j ROT PUT
  -1 STEP
≫ ‘SATLO’ STO

SATLO ( { order }  --  { reorder } )
for j from last downto 2 do:
   let k = random integer in range 0 ≤ k < j
   swap items[j] with items[k]

Input:

[1 2 3 4 5 6] SATLO

Output:

1: [ 2 5 4 6 2 3 ]

Ruby

> class Array
>   def sattolo_cycle!
>     (length - 1).downto(1) do |i|
*       j = rand(i)
>       self[i], self[j] = self[j], self[i]
>     end
>     self
>   end
> end
=> :sattolo_cycle!

> # Tests
> 10.times do
*   p [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].sattolo_cycle!
> end
[10, 6, 9, 7, 8, 1, 3, 2, 5, 4]
[3, 7, 5, 10, 4, 8, 1, 2, 6, 9]
[10, 3, 4, 8, 9, 7, 1, 5, 6, 2]
[8, 7, 4, 2, 6, 9, 1, 5, 10, 3]
[2, 7, 5, 10, 8, 3, 6, 9, 4, 1]
[2, 10, 8, 6, 1, 3, 5, 9, 7, 4]
[8, 5, 6, 1, 4, 9, 2, 10, 7, 3]
[5, 4, 10, 7, 2, 1, 8, 9, 3, 6]
[9, 8, 4, 2, 6, 1, 5, 10, 3, 7]
[9, 4, 2, 7, 6, 1, 10, 3, 8, 5]
=> 10

Run BASIC

a$	= "123456789abcdefghijklmnopqrstuvwxyz"
n	= len(a$)
dim sit$(n)      '  hold area to string
global n

for i = 1 to n			' put string in array
    sit$(i) = mid$(a$,i,1)
next i

call shoSit			' show before change

for i		= n to 1 step -1
    j		= int(i * rnd(1)) + 1
    h$		= sit$(i)
    sit$(i)	= sit$(j)
    sit$(j)	= h$
next i

call shoSit			' show after change
end

sub shoSit
    for i = 1 to n
       print sit$(i);" ";
    next i
    print
end sub

Output:
1 2 3 4 5 6 7 8 9 a b c d e f g h i j k l m n o p q r s t u v w x y z
d c 5 e v 3 n 7 8 h r p 2 y j l s x q 6 f 9 o a u i w 4 1 m g z t k b

Scala

def shuffle[T](a: Array[T]): Array[T] = {
  scala.util.Random.shuffle(a)
  a
}

SequenceL

import <Utilities/Random.sl>;
import <Utilities/Sequence.sl>;

sattolo(x(1), seed) := shuffle(x, seedRandom(seed), size(x));

shuffle(x(1), RG, n) :=
	let
		next := getRandom(RG);
	in
		x when n <= 1 else
		shuffle(swap(x, n, next.Value mod (n - 1) + 1), next.Generator, n - 1);

swap(list(1), i(0), j(0)) := swapHelper(list, i, j, list[i], list[j]);
swapHelper(list(1), i(0), j(0), vali(0), valj(0)) := setElementAt(setElementAt(list, i, valj), j, vali);

Sidef

Modifies the array in-place:

func sattolo_cycle(arr) {
    for i in (arr.len ^.. 1) {
        arr.swap(i, i.irand)
    }
}

Smalltalk

Works with: GNU Smalltalk

SequenceableCollection extend [

    sattoloCycle
        [1 to: self size-1 do:
            [:a || b |
            b := Random between: a+1 and: self size.
            self swap: a with: b]]
]

Modifies the collection in-place. Collections that don't support that, like strings, will throw an exception.

Use example:

st> #() copy sattoloCycle
()
st> #(10) copy sattoloCycle
(10 )
st> #(10 20) copy sattoloCycle
(20 10 )
st> #(10 20 30) copy sattoloCycle
(30 10 20 )
st> #(10 20 30) copy sattoloCycle
(20 30 10 )
st> #(11 12 13 14 15 16 17 18 19 20 21 22) copy sattoloCycle
(22 13 17 18 14 12 15 21 16 11 20 19 )
st> 'Sattolo cycle' asArray sattoloCycle asString
'yocS talcelto'

Swift

extension Array {
  public mutating func satalloShuffle() {
    for i in stride(from: index(before: endIndex), through: 1, by: -1) {
      swapAt(i, .random(in: 0..<i))
    }
  }

  public func satalloShuffled() -> [Element] {
    var arr = Array(self)

    arr.satalloShuffle()

    return arr
  }
}

let testCases = [
  [],
  [10, 20],
  [10, 20, 30],
  [11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22]
]

for testCase in testCases {
  let shuffled = testCase.satalloShuffled()

  guard zip(testCase, shuffled).allSatisfy(!=) else {
    fatalError("satallo shuffle failed")
  }

  print("\(testCase) shuffled = \(shuffled)")
}

Output:

[] shuffled = []
[10, 20] shuffled = [20, 10]
[10, 20, 30] shuffled = [20, 30, 10]
[11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22] shuffled = [20, 22, 17, 12, 19, 14, 15, 13, 21, 16, 11, 18]

Transd

#lang transd

MainModule: {
    // Define an abstract type Vec to make the shuffling
    // function polymorphic
    Vec: typedef(Lambda<:Data Bool>(λ d :Data() 
        (starts-with (_META_type d) "Vector<"))),

    sshuffle: (λ v Vec() locals: rnd 0 
        (for n in Range( (- (size v) 1) 0) do
            (= rnd (randr (to-Int (- n 1))))
            (with tmp (cp (get v n))
                (set-el v n (get v rnd))
                (set-el v rnd tmp))
        )
        (lout v)
    ),
	_start: (λ 
        (with v [10,20,30,40,50,60,70,80,90,100]
            (lout "Original:\n" v)
            (lout "Shuffled:")
            (sshuffle v))
        (lout "")
        (with v ["A","B","C","D","E","F","G","H"]
            (lout "Original:\n" v)
            (lout "Shuffled:")
            (sshuffle (cp v)))
    )
}

Output:

Original:
[10, 20, 30, 40, 50, 60, 70, 80, 90, 100]
Shuffled:
[20, 90, 100, 50, 30, 10, 60, 70, 40, 80]

Original:
["A", "B", "C", "D", "E", "F", "G", "H"]
Shuffled:
["E", "A", "H", "B", "G", "D", "C", "F"]

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;
    }
}

VBA

Private Sub Sattolo(Optional ByRef a As Variant)
    Dim t As Variant, i As Integer
    If Not IsMissing(a) Then
        For i = UBound(a) To lbound(a)+1 Step -1
            j = Int((UBound(a) - 1 - LBound(a) + 1) * Rnd + LBound(a))
            t = a(i)
            a(i) = a(j)
            a(j) = t
        Next i
    End If
End Sub
Public Sub program()
    Dim b As Variant, c As Variant, d As Variant, e As Variant
    Randomize
    'imagine an empty array on this line
    b = [{10}]
    c = [{10, 20}]
    d = [{10, 20, 30}]
    e = [{11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22}]
    f = [{"This ", "is ", "a ", "test"}]
    Debug.Print "Before:"
    Sattolo 'feeding an empty array ;)
    Debug.Print "After: "
    Debug.Print "Before:";
    For Each i In b: Debug.Print i;: Next i: Debug.Print
    Sattolo b
    Debug.Print "After: ";
    For Each i In b: Debug.Print i;: Next i: Debug.Print
    Debug.Print "Before:";
    For Each i In c: Debug.Print i;: Next i: Debug.Print
    Sattolo c
    Debug.Print "After: ";
    For Each i In c: Debug.Print i;: Next i: Debug.Print
    Debug.Print "Before:";
    For Each i In d: Debug.Print i;: Next i: Debug.Print
    Sattolo d
    Debug.Print "After: ";
    For Each i In d: Debug.Print i;: Next i: Debug.Print
    Debug.Print "Before:";
    For Each i In e: Debug.Print i;: Next i: Debug.Print
    Sattolo e
    Debug.Print "After: ";
    For Each i In e: Debug.Print i;: Next i: Debug.Print
    Debug.Print "Before:";
    For Each i In f: Debug.Print i;: Next i: Debug.Print
    Sattolo f
    Debug.Print "After: ";
    For Each i In f: Debug.Print i;: Next i: Debug.Print
End Sub

Output:

Before:

After: Before: 10 After: 10 Before: 10 20 After: 20 10 Before: 10 20 30 After: 20 10 30 Before: 11 12 13 14 15 16 17 18 19 20 21 22 After: 16 18 19 17 12 20 22 14 11 13 15 21 Before:This is a test After: testa is This

Wren

import "random" for Random

var rand = Random.new()

var sattolo = Fn.new { |items|
    var count = items.count
    if (count < 2) return
    for (i in count-1..1) {
        var j = rand.int(i)
        var t = items[i]
        items[i] = items[j]
        items[j] = t
    }
}

var tests = [[], [10], [10, 20], [10, 20, 30], [11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22], 
    ["a", "b", "c", "d", "e"], ["fgh", "ijk", "lmn", "opq", "rst", "uvw", "xyz"] ] 
for (test in tests) {
    System.print("Original: %(test)")
    sattolo.call(test)
    System.print("Sattolo : %(test)\n")
}

Output:

Sample run:

Original: []
Sattolo : []

Original: [10]
Sattolo : [10]

Original: [10, 20]
Sattolo : [20, 10]

Original: [10, 20, 30]
Sattolo : [20, 30, 10]

Original: [11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22]
Sattolo : [21, 22, 19, 15, 13, 12, 11, 14, 20, 16, 18, 17]

Original: [a, b, c, d, e]
Sattolo : [b, e, d, a, c]

Original: [fgh, ijk, lmn, opq, rst, uvw, xyz]
Sattolo : [xyz, opq, rst, fgh, ijk, lmn, uvw]

XPL0

proc Sattolo(Array, Items, BytesPerItem);
int  Array, Items, BytesPerItem;
int  I, J;
char Temp(8);
[for I:= Items-1 downto 1 do
    [J:= Ran(I);        \range [0..I-1]
    CopyMem(Temp, Array+I*BytesPerItem, BytesPerItem);
    CopyMem(Array+I*BytesPerItem, Array+J*BytesPerItem, BytesPerItem);
    CopyMem(Array+J*BytesPerItem, Temp, BytesPerItem);
    ];
];

string 0;       \use zero-terminated strings
int A;  char B;  real C;
int I;
[A:= [1, 2, 3, 4, 5];
Sattolo(A, 5, 4 \bytes per int\);
for I:= 0 to 5-1 do
    [IntOut(0, A(I));  ChOut(0, ^ )];
CrLf(0);
B:= "12345";
Sattolo(B, 5, 1 \byte per char\);
for I:= 0 to 5-1 do
    [ChOut(0, B(I));  ChOut(0, ^ )];
CrLf(0);
C:= [1., 2., 3., 4., 5.];
Sattolo(addr C(0), 5, 8 \bytes per real\);
for I:= 0 to 5-1 do
    [RlOut(0, C(I));  ChOut(0, ^ )];
CrLf(0);
A:= [10];
Sattolo(A, 1, 4 \bytes per int\);
for I:= 0 to 1-1 do
    [IntOut(0, A(I));  ChOut(0, ^ )];
CrLf(0);
]

Output:

2 5 1 3 4 
5 1 4 2 3 
    5.00000     4.00000     1.00000     3.00000     2.00000 
10

Yabasic

sub sattolo$(l$)
    local i, j, items$(1), n, t$
    
    n = token(l$, items$(), ",")
    
    for i = n to 2 step -1
        j = int(ran(i - 1)) + 1
        t$ = items$(i)
        items$(i) = items$(j)
        items$(j) = t$
    next

    t$ = ""
    for i = 1 to n
    	t$ = t$ + items$(i) + ","
    next
    return left$(t$, len(t$) - 1)
end sub
 
data "", "10", "10,20", "10,20,30", "11,12,13,14,15,16,17,18,19,20,21,22"

for n = 1 to 5
    read item$ : print "[", sattolo$(item$), "]"
next

zkl

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

sattoloCycle([0..9].walk().copy()).println();
sattoloCycle("this is a test".split()).println();

Output:

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