Java/src/main/java/com/thealgorithms/maths/KrishnamurthyNumber.java

package com.thealgorithms.maths;

/* This is a program to check if a number is a Krishnamurthy number or not.
A number is a Krishnamurthy number if the sum of the factorials of the digits of the number is equal to the number itself.
For example, 1, 2 and 145 are Krishnamurthy numbers.
Krishnamurthy number is also referred to as a Strong number.
 */
import java.io.*;

public class KrishnamurthyNumber {

    //returns True if the number is a Krishnamurthy number and False if it is not.

    public static boolean isKMurthy(int n) {
        //initialising the variable s that will store the sum of the factorials of the digits to 0
        int s = 0;
        //storing the number n in a temporary variable tmp
        int tmp = n;

        //Krishnamurthy numbers are positive
        if (n <= 0) {
            return false;
        } //checking if the number is a Krishnamurthy number
        else {
            while (n != 0) {
                //initialising the variable fact that will store the factorials of the digits
                int fact = 1;
                //computing factorial of each digit
                for (int i = 1; i <= n % 10; i++) {
                    fact = fact * i;
                }
                //computing the sum of the factorials
                s = s + fact;
                //discarding the digit for which factorial has been calculated
                n = n / 10;
            }

            //evaluating if sum of the factorials of the digits equals the number itself
            if (tmp == s) {
                return true;
            } else {
                return false;
            }
        }
    }

    public static void main(String args[]) throws IOException {
        BufferedReader br = new BufferedReader(
            new InputStreamReader(System.in)
        );
        System.out.println(
            "Enter a number to check if it is a Krishnamurthy number: "
        );
        int n = Integer.parseInt(br.readLine());
        if (isKMurthy(n)) {
            System.out.println(n + " is a Krishnamurthy number.");
        } else {
            System.out.println(n + " is NOT a Krishnamurthy number.");
        }
    }
}