We will go through kotlin program to reverse a number.

For example,

Input:
1234

Output:
4321

Input:
1232

Output:
2321

1. Program to Reverse a number

Sourcecode –

import java.util.*

fun main() {

    val read = Scanner(System.`in`)

    println("Enter n:")
    var n = read.nextInt()

    var reverseN = 0
    while (n != 0) {
        val remainder = n % 10
        reverseN = reverseN * 10 + remainder
        n /= 10
    }

    println("Reversed N = $reverseN")
}

When you run the program, output will be

Enter n:
12345
Reversed N = 54321

Explanation:

Let’s assume we have entered n = 123

Now,

At 1st iteration,
n = 123, reverseN = 0

(123 != 0) is true. So, while loop will be executed.
Inside while loop,
remainder = 123 % 10 => remainder = 3
reverseN = reverseN * 10 + remainder => reverseN = 0 * 10 + 3 => reverseN = 3
n /= 10 => n = n / 10 => n = 123 / 10 => n = 12

After 1st iteration,
n = 12, reverseN = 3

At 2nd iteration,
n = 12, reverseN = 3

(12 != 0) is true. So, while loop will be executed.
Inside while loop,
remainder = 12 % 10 => remainder = 2
reverseN = reverseN * 10 + remainder => reverseN = 3 * 10 + 2 => reverseN = 32
n = n / 10 => n = 12 / 10 => n = 1

After 2nd iteration,
n = 1, reverseN = 32

At 3rd iteration,
n = 1, reverseN = 32

(1 != 0) is true. So, while loop will be executed.
Inside while loop,
remainder = 1 % 10 => remainder = 1
reverseN = reverseN * 10 + remainder => reverseN = 32 * 10 + 1 => reverseN = 321
n = n / 10 => n = 1 / 10 => n = 0

After 3rd iteration,
n = 0, reverseN = 321

At 4th iteration,
n = 0, reverseN = 321

(0 != 0) is false. So, while loop will be exited.

So, finally reverseN is our reversed number for given number.

You can apply the same logic for any other number.

Thus, we went through Kotlin program to reverse a number