ArmstrongNumber.java

import java.util.*;

public class ArmstrongNumber
{
    static int length_number(int num){
        return String.valueOf(num).length();
    }
	public static void main(String[] args) {
	    Scanner sc = new Scanner(System.in);
	    System.out.print("Enter a number : ");
	    int num = sc.nextInt();
	    int res = num;
	    int val = 0;
	    int len = length_number(num);
	    while(res>0){
	        int temp = res % 10;
	        val += Math.pow(temp, len);
	        res = res / 10;
	    }
	    if(num == val) System.out.println(num+" is an armstrong number.");
	    else System.out.println(num+" is not an armstrong number.");
	}
}

/*
Sample input and output
Example 1:
Enter a number : 1002
Number is not an armstrong number.

Example 2:
Enter a number : 153
Number is an armstrong number.

Example 3:
Enter a number : 8208
8208 is an armstrong number.

Complexities
time: O(log(n))
space: O(1)
*/