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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

1. Bubble Sort Algorithm in Kotlin
2. Heap Sort Algorithm in Kotlin
3. Insertion Sort Algorithm in Kotlin
4. Merge Sort Algorithm in Kotlin
5. Quick Sort Algorithm in Kotlin
6. Selection Sort Algorithm in Kotlin
7. Stack Data Structure Implementation in Kotlin
   
8. Queue Data Structure Implementation in Kotlin
   
9. Deque Implementation in Kotlin
   
10. Singly Linked List Implementation in Kotlin
    
11. Doubly Linked List Implementation in Kotlin
    
12. Circular Linked List Implementation in Kotlin