Java Program to Check If a Number is an Amstrong Number

Java program to check if a number is an amstrong number has been shown here. A positive integer of order n is called an amstrong number if the sum of each digit to the power n is equal to that number.

For example, 153 and 1634 are amstrong numbers as $153 = 1^3 + 5^3 + 3^3$ and $1634 = 1^4 + 6^4 + 3^4 + 4^4$.

The algorithm, pseudocode and time complexity of the program have been shown below.

Page contents:

1. Algorithm

2. Pseudocode

3. Time Complexity

4. Program & Output

1. Algorithm to check if a number is an amstrong number

1. Take input of a positive number n.

2. Calculate d, the total no of digit of n

3. Extract each digit $p_i$ and perform sum = $\sum_{i=1}^d p_i ^d $

4. Check If sum == n

5. If step 4 is true, then display n as an amstrong number

6. If step 4 is false, then display n as not an amstrong number

2. Pseudocode to check if a number is an amstrong number

Input : A postive number $n$ as input

Output : $n$ is an amstrong number or not an amstrong number

1. Procedure checkAmstrong($n$):

2. $t \leftarrow n$:

3. $sum \leftarrow 0$:

4. Count $d$, the total no of digits in $n$

5. Repeat until $t != 0$

6. $r \leftarrow t \mod 10$

7. $sum \leftarrow sum + r^d$

8. $t \leftarrow t / 10$

9. If $sum \mod n$ == 0:

10. Return "Amstrong number"

11. Else:

12. Return "Not an amstrong number"

13. End Procedure

3. Time complexity to check if a number is an amstrong number

Time Complexity: O(log(n))

Where log(n) is the total no of digits of the input number n.

4. Java Program & output to check if a number is an amstrong number

Code has been copied

/**********************************
	 alphabetacoder.com
Java program to check if a number 
is an amstrong number or not
***********************************/

import java.util.Scanner;
import java.lang.Math;

class Main {
    public static void main(String args[]) {
        // declare instance of Scanner class
        Scanner sc = new Scanner(System.in);

        // declare variables
        int n, d = 0, t, r, sum = 0;

        // take input
        System.out.print("Enter the number = ");
        n = sc.nextInt();

        // copy value
        t = n;
        // calculate the number of digit 
        while (t != 0) {
            d++;
            t = t / 10;
        }

        // copy value
        t = n;
        // find the sum of digits each to the power d
        while (t != 0) {
            r = t % 10;
            sum = sum + (int) Math.pow(r, d);
            t = t / 10;
        }

        //check if input number is amstrong or not
        if (n == sum)
            System.out.println(n + " is an amstrong number!");
        else
            System.out.println(n + " is not an amstrong number!");
    }
}

Output

Enter the number = 153

153 is an amstrong number!