Logo

Programming-Idioms

# 10 Shuffle a list
Generate a random permutation of the elements of list x
New implementation

Be concise.

Be useful.

All contributions dictatorially edited by webmasters to match personal tastes.

Please do not paste any copyright violating material.

Please try to avoid dependencies to third-party libraries and frameworks.

Other implementations 
#include <stdlib.h>
#include <time.h>
srand(time(NULL));
for (int i = 0; i < N-1; ++i)
{
    int j = rand() % (N-i) + i;
    int temp = x[i];
    x[i] = x[j];
    x[j] = temp;
}
(shuffle x)
#include <algorithm>
#include <vector>
std::random_shuffle(x.begin(), x.end());
using System;
using System.Collections.Generic;
private static Random rng = new Random();  

public static void Shuffle<T>(this IList<T> x)  
{  
    int n = x.Count;  
    while (n > 1) {  
        n--;  
        int k = rng.Next(n + 1);  
        T value = x[k];  
        x[k] = x[n];  
        x[n] = value;  
    }  
}
using System;
using System.Collections.Generic;
using System.Linq;
public static IEnumerable<T> Shuffle<T>(this IEnumerable<T> input)
    => input.OrderBy(_ => Guid.NewGuid());

import std.random;
randomShuffle(x);
x.shuffle();
var shuffled = x.toList()..shuffle();
y = Enum.shuffle x
[Y||{_,Y} <- lists:sort([ {rand:uniform(), N} || N <- X])].
module M_shuffle
contains
function scramble( number_of_values ) result(array)
   integer,intent(in)    :: number_of_values
   integer,allocatable   :: array(:)
   array=[(i,i=1,number_of_values)]
   n=1; m=number_of_values
   do k=1,2
    do i=1,m
     call random_number(u)
     j = n + FLOOR((m+1-n)*u)
     itemp=array(j); array(j)=array(i); array(i)=itemp
    enddo
   enddo
end function scramble
end module M_shuffle
 :
use M_shuffle, only : scramble
newlist=list(scramble(size(list))

import "math/rand"
for i := len(x) - 1; i > 0; i-- {
	j := rand.Intn(i + 1)
	x[i], x[j] = x[j], x[i]
}
import "math/rand"
y := make([]T, len(x))
perm := rand.Perm(len(x))
for i, v := range perm {
	y[v] = x[i]
}
import "math/rand"
rand.Shuffle(len(x), func(i, j int) {
	x[i], x[j] = x[j], x[i]
})
import "math/rand"
for i := range x {
	j := rand.Intn(i + 1)
	x[i], x[j] = x[j], x[i]
}
x.shuffle()
shuffle x = if length x < 2 then return x else do
	i <- System.Random.randomRIO (0, length(x)-1)
	r <- shuffle (take i x ++ drop (i+1) x)
	return (x!!i : r)

for (var i = x.length - 1; i > 0; i--) {
    var j = Math.floor(Math.random() * (i + 1));
    var temp = x[j];
    x[j] = x[i];
    x[i] = temp;
}
import java.util.Collections;
Collections.shuffle(x);
x.shuffle()
val y = x.shuffled()
(let ((end (length x)))
 (loop for i from 0 below end
       do (rotatef (aref x i)
                   (aref x (+ i (random (- end i)))))))

shuffled = {}
for i, v in ipairs(x) do
	local pos = math.random(1, #shuffled+1)
	table.insert(shuffled, pos, v)
end
function(x)
	for i = #x, 2, -1 do
		local j = math.random(i)
		x[i], x[j] = x[j], x[i]
	end
end

@import GameplayKit;
x.shuffledArray
shuffle($x);
var Iter,rr: integer; 
[...]
  for Iter := 0 to high(x) do
    begin
      rr := random(high(x))+1;
      tmp := x[Iter];
      x[Iter] := x[rr];
      x[rr] := tmp;
    end;
use List::Util 'shuffle';
@shuffled = shuffle(@x);
import random
random.shuffle(x)
from random import shuffle
shuffle(x)
y = x.shuffle
use rand::seq::SliceRandom;
use rand::thread_rng;
let mut rng = thread_rng();
x.shuffle(&mut rng);
extern crate rand;
use rand::{Rng, StdRng};
let mut rng = StdRng::new().unwrap();
rng.shuffle(&mut x);
import scala.util.Random
val shuffled = Random.shuffle(x)
(shuffle x)
(define shuffle
  (lambda (x)
    (if (< (length x) 2) 
        list
        (let ((item (list-ref list (random (length x)))))
          (cons item (shuffle (remove item x)))))))
x shuffled.
Function Shuffle(Of T)(collection As IEnumerable(Of T)) As List(Of T)
    Dim r As Random = New Random()
    Shuffle = collection.OrderBy(Function(a) r.Next()).ToList()
End Function

Preview