Submission

Score: 100

User: pond4545

Problemset: ตรวจบัตรเครดิต

Language: cpp

Time: 0.003 second

Submitted On: 2025-10-08 11:08:00

#include <iostream>
#include <string>
using namespace std;

int main()
{
    string credit;
    cin >> credit;

    int sum = 0;
    int len = credit.length();
    int check = credit[len - 1] - '0'; // last digit is the check digit

    // process digits from right to left (excluding check digit)
    for (int i = len - 2, pos = 1; i >= 0; i--, pos++) {
        int n = credit[i] - '0'; // convert char to int
        if (pos % 2 == 1) { // every second digit from right
            n *= 2;
            if (n > 9) n = n / 10 + n % 10;
        }
        sum += n;
    }

    int verify = (10 - (sum % 10)) % 10;

    if (verify == check)
        cout << "yes";
    else
        cout << "no";

    return 0;
}