Sort array in decreasing order in Kotlin

This article explores different ways to sort the array in decreasing order in Kotlin.

1. Using `sortedArrayDescending()` function

The standard solution to sort a primitive array or a generic array is using the sortedArrayDescending() function. It returns an array with all elements sorted in descending order. This is demonstrated below for an IntArray:

fun main() {

val array: IntArray = intArrayOf(3, 1, 2, 5, 4)

val sortedDesc = array.sortedArrayDescending()

println(sortedDesc.contentToString()) // [5, 4, 3, 2, 1]

}

Download Code

This works for both primitive and generic arrays. Note that this results in a new sorted array, and the original array remains unchanged.

fun main() {

val array: Array<Int> = arrayOf(3, 1, 2, 5, 4)

val sortedDesc = array.sortedArrayDescending()

println(sortedDesc.contentToString()) // [5, 4, 3, 2, 1]

}

Download Code

2. Using `sortedByDescending()` function

Another plausible, but a less efficient solution, is to sort the array in descending order using the sortedByDescending() function. This also works for both primitive and generic arrays and returns a “list” in reverse order. The following code demonstrates this:

fun main() {

val array: IntArray = intArrayOf(3, 1, 2, 5, 4)

val sortedDesc: List<Int> = array.sortedByDescending { it }

println(sortedDesc) // [5, 4, 3, 2, 1]

}

Download Code

You can invoke the corresponding to*Array() function to convert the list back into an array.

fun main() {

val array: IntArray = intArrayOf(3, 1, 2, 5, 4)

val sortedDesc = array

.sortedByDescending { it } // List<Int>

.toIntArray() // IntArray

println(sortedDesc.contentToString()) // [5, 4, 3, 2, 1]

}

Download Code

3. Using `sortWith()` function

Another good alternative is to use the sortWith() function to in-place sort a generic array according to the specified comparator. This assumes that all array elements are mutually comparable by the comparator. The following example demonstrates this:

fun main() {

val array = arrayOf(3, 1, 2, 5, 4)

array.sortWith(reverseOrder())

println(array.contentToString()) // [5, 4, 3, 2, 1]

}

Download Code

This only works with a typed array, and won’t work with an array of primitives. To “inplace” sort a primitive array, use some standard sorting algorithm like Quicksort, Merge Sort, etc.

That’s all about sorting the array in decreasing order in Kotlin.

Sort array in decreasing order in Kotlin

1. Using sortedArrayDescending() function

2. Using sortedByDescending() function

3. Using sortWith() function

Share this:

1. Using `sortedArrayDescending()` function

2. Using `sortedByDescending()` function

3. Using `sortWith()` function