Shuffle a list in Kotlin

This article explores different ways to shuffle a list in Kotlin.

1. Using `shuffle()` function

The simplest and fairly efficient solution is to randomize a list is to use the native function shuffle().

fun <T> shuffle(list: MutableList<T>) {

list.shuffle()

}

fun main() {

val list: MutableList<Int?> = (0..10).toMutableList();

shuffle(list)

println(list)

}

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2. Using Fisher–Yates Shuffle Algorithm

Following is an implementation of Fisher–Yates shuffle algorithm, which shuffles the list from the highest index to the lowest index:

import kotlin.random.Random

fun <T> shuffle(list: MutableList<T>)

{

// start from the end of the list

for (i in list.size - 1 downTo 1)

{

// get a random index `j` such that `0 <= j <= i`

val j = Random.nextInt(i + 1)

// swap element at i'th position in the list with the element at j'th position

val temp = list[i]

list[i] = list[j]

list[j] = temp

}

fun main() {

val list: MutableList<Int?> = (0..10).toMutableList();

shuffle(list)

println(list)

}

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The following is an equivalent version of the Fisher-Yates Shuffle algorithm, which shuffles the list from the lowest index to the highest index:

import kotlin.random.Random

fun <T> shuffle(list: MutableList<T>)

{

// start from the beginning of the list

for (i in 0 until list.size - 1)

{

// get a random index `j` such that `i <= j <= n`

val j = i + Random.nextInt(list.size - i)

// swap element at i'th position in the list with the element at j'th position

val temp = list[i]

list[i] = list[j]

list[j] = temp

}

fun main() {

val list: MutableList<Int?> = (0..10).toMutableList();

shuffle(list)

println(list)

}

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That’s all about shuffling a list in Kotlin.

1. Using shuffle() function

2. Using Fisher–Yates Shuffle Algorithm

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1. Using `shuffle()` function