CareerCup

#include<iostream>
using namespace std;
int main()
{

long int a;
cin>>a;

int last= a%10;
int sum=0;
a=a/10;
int temp;
while(a!=0)
{

temp=a%10;
temp*=temp;
temp%=10;
sum+=temp;
sum%=10;

a=a/10;


}

if(last== sum)
{

cout<<"valid";

}
else
{
cout<<"invalid";
}
}

no need to use this segment of code :: temp%=temp;

main()
{
int i,last,q,s,sum=0;
printf("enter");
scanf("%d",&i);
q=i/10;
last=i%10;
while(q)
{
s=q%10;
sum=sum+s*s;
q=q/10;
}

if(last==(sum%10))
printf("valid");
else
printf("invalid");
getch();
}

public class Checksum {

public static void main(String[] args) {
String num = "321541";
char[] ch = num.toCharArray();
int mult = 0;
for (int i = 0; i < ch.length - 1; i++) {
int val = ch[i] - '0';
mult += val * val;
}
int t = checkCheckSum(mult);
if (t == ch[num.length() - 1]-'0') {
System.out.println("Check Sum Valid");
} else {
System.out.println("Check Sum Invalid :: " + t);
}
}

private static int checkCheckSum(int number) {
String mul = String.valueOf(number);
while (mul.length() > 1) {
char a[] = mul.toCharArray();
int sum = 0;
for (Character c : a) {
int v = c - '0';
sum = sum + v;
}
mul=String.valueOf(sum);
}
return Integer.parseInt(mul);
}
}

package Interview_Specific;

import java.util.Scanner;

/**
 * Created by GOOGLE on 8/21/2015.
 */
public class ValidChecksum {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.println("--------PLEASE ENTER INPUT CHECKSUM-------\n");
        int inputNum = in.nextInt();
        int lastDigit = (inputNum % 10);
        System.out.println("last digit: " + lastDigit);
        int remainingNum = (inputNum / 10);
        System.out.println("remaining number: " + remainingNum);
        int checksum = 0;
        while ((remainingNum % 10) > 0) {
            checksum = checksum + calculatePower((remainingNum % 10), 2);
            System.out.println("checksum at this point of time: " + checksum);
            remainingNum = remainingNum / 10;
        }
        if (checksum == calculatePower(lastDigit, 2))
            System.out.println("----CHECKSUM IS VALID----" + checksum);
        else
            System.out.println("----CHECKSUM IS INVALID----" + checksum);
    }

    private static int calculatePower(int i, int j) {
        System.out.println("value of i and j :" + i + " " + j);
        if (j == 0)
            return 1;
        else {
            i = i * calculatePower(i, --j);
        }
        System.out.println("final value of power: " + i);
        return i;
    }
}