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In this tutorial, we will write a Program to implement the Merge Sort algorithm in Kotlin programming language.

Merge sort is one of the most efficient sorting algorithms. With a time complexity of O(n log n), it’s one of the fastest of all general-purpose sorting algorithms.

The idea behind merge sort is divide and conquer — to break a big problem into several smaller, easier-to-solve problems, and then combine those solutions into a final result. The merge sort mantra is to split first and merge after.

Merge Sort Algorithm in Kotlin

Let's write the Kotlin program to Sort an Array of elements in ascending order:

import java.util.*

fun <E: Comparable<E>> Array<E>.sort(): Array<E> {
    if (size <= 1) return this

    val middle = size / 2
    val left = copyOfRange(0, middle)
    val right = copyOfRange(middle, size)
    return merge(this, left.sort(), right.sort())
}

private fun <E: Comparable<E>> merge(arr: Array<E>, left: Array<E>, right: Array<E>): Array<E> {
    val leftArrSize = left.size
    val rightArrSize = right.size
    var leftArrIndex = 0
    var rightArrIndex = 0
    var index = 0
    while(leftArrIndex < leftArrSize && rightArrIndex < rightArrSize) {
        if (left[leftArrIndex] <= right[rightArrIndex]) {
            arr[index] = left[leftArrIndex]
            leftArrIndex++
        } else {
            arr[index] = right[rightArrIndex]
            rightArrIndex++
        }
        index++
    }

    while(leftArrIndex < leftArrSize) {
        arr[index] = left[leftArrIndex]
        leftArrIndex++
        index++
    }

    while(rightArrIndex < rightArrSize) {
        arr[index] = right[rightArrIndex]
        rightArrIndex++
        index++
    }
    return arr
}

fun main(args: Array<String>) {
    val nums = arrayOf(2, 12, 89, 23, 76, 43, 12)
    nums.sort()
    println(Arrays.toString(nums))

    val languages = arrayOf("Kotlin", "Java", "C#", "R", "Python", "Scala", "Groovy", "C", "C++")
    val sortedLanguages = languages.sort()
    println(Arrays.toString(languages))
}

Output:

[2, 12, 12, 23, 43, 76, 89]
[C, C#, C++, Groovy, Java, Kotlin, Python, R, Scala]

Related Data Structures and Algorithms in Kotlin

Bubble Sort Algorithm in Kotlin
Heap Sort Algorithm in Kotlin
Insertion Sort Algorithm in Kotlin
Merge Sort Algorithm in Kotlin
Quick Sort Algorithm in Kotlin
Selection Sort Algorithm in Kotlin
Stack Data Structure Implementation in Kotlin
Queue Data Structure Implementation in Kotlin
Deque Implementation in Kotlin
Singly Linked List Implementation in Kotlin
Doubly Linked List Implementation in Kotlin
Circular Linked List Implementation in Kotlin

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