Write a Kotlin Program to Check A Number is Armstrong number or not

What is Armstrong Number ?

A positive integer (x) of n digits is called armstrong number of order n (number of digits in x) if

abcd... = pow(a,n) + pow(b,n) + pow(c,n) + pow(d,n) + ....

Note that abcd… is number x where a, b, c, d ….etc. are it’s digits. n is number of digits in x.

For Example,

Input:
120

Output:
No, 120 is not armstrong number.

Input:
423432

Output:
No, 423432 is not armstrong number.

Input:
153

Output:
Yes, 153 is armstrong number.

1. Program to Check Armstrong Number

Sourcecode –

import java.util.*
import kotlin.math.floor
import kotlin.math.log10
import kotlin.math.pow
import kotlin.math.roundToInt

fun main() {
    val read = Scanner(System.`in`)

    println("Enter x:")
    val x = read.nextInt()

    if(checkArmstrong(x)) {
        println("Yes, $x is armstrong number.")
    } else {
        println("No, $x is not armstrong number.")
    }
}

private fun checkArmstrong(number: Int): Boolean {

    // Get the count of digits in number
    val n = floor(log10(number.toDouble()) + 1).roundToInt()

    var x = number

    // Find sum by power last digit in n to count.
    var sum = 0
    while(x > 0) {
        val digit = x % 10
        sum = (sum + (digit.toDouble().pow(n))).roundToInt()
        x /= 10
    }

    // Return true if sum is equal to number
    return sum == number
}

When you run the program, output will be –

Enter n:
1634
Yes, 1634 is armstrong number.

Explanation:

Here, we have created an object of Scanner. Scanner takes an argument which says where to take input from.
System.`in` means take input from standard input – Keyboard.

read.nextIn() means read anything entered by user before space or line break from standard input – Keyboard.

Stored the value read using nextInt() in variable x

We defined 1 additional functional –

• checkArmstrong: returns true if number passed as argument is Armstrong Number. Else, returns false.

Inside checkArmstrong function,

• Count number of digits and store in variable n
• Then, For every digit r in number x, compute r^n

For example,

For x = 153
n = 3.

Now, run a while loop till x != 0

For x = 153,
digit = x % 10 => digit = 153 % 10 => digit = 3
sum = (sum + (digit.pow(n))) => sum = 0 + 3^3 => sum = 27
x /= 10 => x = 15

For x = 15,
digit = x % 10 => digit = 15 % 10 => digit = 5
sum = (sum + (digit.pow(n))) => sum = 27 + 5^3 => sum = 27 + 125 => sum = 152
x /= 10 => x = 1

For x = 1,
digit = x % 10 => digit = 1 % 10 => digit = 1
sum = (sum + (digit.pow(n))) => sum = 152 + 1^3 => sum = 152 + 1 => sum = 153
x /= 10 => x = 0

At x = 0 , condition 0 != 0 is false.
So, while loop is terminated.

Thus, we went through Kotlin Program to check if given number is armstrong number or not.