# Validate Credit Card Number [6 kyu]

[Validate Credit Card Number](https://www.codewars.com/kata/5418a1dd6d8216e18a0012b2)
6 kyu

## Solution

/**
*** Author: R-CO
*** E-Mail: [e-mail]
*** Date: 2020-08-05
**/
#include <cctype>
#include <cstdlib>
#include <iostream>
using std::cout;
using std::endl;
#include <vector>

struct TestCaseStruct {
  int input;
  bool expected_output;
};

class Kata {
 public:
  static bool validate(long long int n) {
    auto digits = SplitToDigits(n);

    for (size_t index = 1; index < digits.size(); index += 2) {
      digits[index] <<= 1;
      if (digits[index] > 9) {
        digits[index] -= 9;
      }
    }

    int sum = 0;
    for (const auto digit : digits) {
      sum += digit;
    }

		if (sum % 10 != 0) {
      return false;
		}

    return true;
  }

 private:
  static std::vector<int> SplitToDigits(long long int n) {
    int base = 1;
    std::vector<int> digits;
    do {
      base *= 10;
      digits.push_back(n % 10);
      n /= 10;
    } while (n > 0);

    return digits;
  }
};

int main(int argc, char *argv[]) {
  /*
   */
  TestCaseStruct test_cases[] = {{891, false}, {2121, true}};

  Kata solution;
  for (const auto &test_case : test_cases) {
    if (solution.validate(test_case.input) == test_case.expected_output) {
      cout << "test case \"" << test_case.input << "\" is pass." << std::endl;
    } else {
      cout << "test case \"" << test_case.input << "\" is fail." << std::endl;
    }
  }

  return EXIT_SUCCESS;
}

## Result


###### tags: `CodeWars` `C++`