Iterate over a string backward in Kotlin

This article explores different ways to iterate over a string backward in Kotlin.

1. Using for loop

You can use a simple for-loop to process each character of the string in the reverse direction. This approach is very effective for strings having fewer characters.

fun main() {

val s = "Reverse String"

// using simple for-loop

for (i in s.length - 1 downTo 0) {

print(s[i])

}

Download Code

2. Convert to character array

In this approach, you initially reverse the string. Then you convert the reversed String to a character array by using the String.toCharArray() function. Finally, you iterate the char[] using a foreach loop, as shown below:

fun main() {

val s = "Reverse String"

// reverse the string and convert it to `char[]` array

val chars = StringBuilder(s).reverse().toString()

.toCharArray()

// iterate over char[] using the foreach loop

for (ch in chars) {

print(ch)

}

Download Code

3. Using `CharacterIterator`

You can also use the CharacterIterator interface that provides bidirectional iteration for a String.

import java.text.CharacterIterator

import java.text.StringCharacterIterator

// Traverse the string backward, from end to start

fun traverseBackwards(itr: CharacterIterator) {

var ch = itr.last()

while (ch != CharacterIterator.DONE)

{

print(ch)

ch = itr.previous()

}

fun main() {

val s = "Reverse String"

val it: CharacterIterator = StringCharacterIterator(s)

traverseBackwards(it)

}

Download Code

4. Using `String.Split()` function

String.split() splits the specified string and returns an array of strings created by splitting this string.

fun main() {

val s = "Reverse String"

val arr = s.split("".toRegex()).toTypedArray()

for (i in arr.indices.reversed()) {

print(arr[i])

}

Download Code

That’s all about iterating over a string backward in Kotlin.

Iterate over a string backward in Kotlin

1. Using for loop

2. Convert to character array

3. Using CharacterIterator

4. Using String.Split() function

Share this:

3. Using `CharacterIterator`

4. Using `String.Split()` function