Program to reverse a string in kotlin

In this article, you will learn to reverse a string in different ways. We will learn step by step, how to reverse a string in Kotlin.


1. Reverse a string in Kotlin using for loop
Source Code:

fun main(args: Array<String>)
{
    val str = "Hello World"
    var charOfString  = ""
    for (i in 0..str.length - 1)
    {
        charOfString += str[str.length - 1 -i].toString()
    }
    print("Reversed String: $charOfString")
}

Output:

Reversed String: dlroW olleH

Reverse a string in kotlin using for loop - output

Description:
In the above program, we have used for loop to reverse a string. First, we have stored the string in str variable which we want to reverse.

In a next line, for loop will iterate until str.length - 1. With each iteration, it will find the value of a string using str[str.length - 1 -i]. Same will be printed using print() function.

2. Reverse a string in Kotlin using recursion

Source Code:

fun main(args: Array<String>) {

    val sentence = "Hello World"

    val reversed = reverse(sentence)

    println("The reversed sentence is: $reversed")

}

fun reverse(sentence: String): String

{

    if (sentence.isEmpty())

    {

        return sentence

    }

    return reverse(sentence.substring(1)) + sentence[0]

}

Output:

The reversed sentence is: dlroW olleH

Reverse a string in kotlin using recursion - output

Description:

In the above program, we have used recursion to reverse the sentence string. Here we have written new function reverse(sentence: String): String, which takes a string input and returns string output.

Next, we have called reverse function and passed a string which wanted to reverse. As you can see inside the reverse() function we have called the function reverse(sentence.substring(1)) itself. It will recursively call itself until a string is empty sentence.isEmpty().