Lab 1 - Luhn's Algorithm

import java.util.*;

 

public class Solution {

    public static void main(String args[] ) throws Exception {

        Scanner myscanner = new Scanner(System.in);

        String number = myscanner.nextLine();

        int total=0;

        for(int i=0;i<number.length()-1;i++){

            int digit = Integer.parseInt(""+number.charAt(number.length()-i-2));

            if(i%2==0){

                digit=digit*2;

            }

            if(digit>9){

                digit=digit-9;

            }

            total+=digit;

        }

        if((total+Integer.parseInt(""+number.charAt(number.length()-1)))%10==0){

            System.out.println("VALID");

        }else{

            System.out.println("INVALID");

        }

    }

}