/* - This program requires you to type in a long integer to test if it is a valid credit card number. - I actually came up with this code through completing someone else's assignments. =^= - Original Author : Hatsy Rei - DO NOT STEAL MY COOKIES! */ #include #include using namespace std; bool isValid(long long int c_card_num); int main() { long long int c_card_num; int array[20]; int i; int num_sum = 0; int num_sum2 = 0; int final_sum; int count = 0; cin >> c_card_num; if (!(isValid(c_card_num))) { cout << "The credit card number is not valid." << endl; return 0; } while (c_card_num != 0) { i = c_card_num % 10; array[count] = i; c_card_num -= i; c_card_num /= 10; count++; } i = 0; for (int j = 1; j < count; j+=2) { array[j] *= 2; if (array[j] > 9) { i = array[j] % 10; array[j] -= i; array[j] /= 10; array[j] += i; } num_sum += array[j]; num_sum2 += array[j-1]; } final_sum = num_sum + num_sum2; if (final_sum % 10 == 0) { cout << "The credit card number is valid." << endl << endl; } else { cout << "The credit card number is not valid" << endl << endl; } return 0; } bool isValid(long long int c_card_num) { int i = 0; int count = 0; int temp_array[20]; while (c_card_num != 0) { i = c_card_num % 10; temp_array[count] = i; c_card_num -= i; c_card_num /= 10; count++; } if (count >= 13 && count <= 16) { if (temp_array[count - 1] == 4 || temp_array[count - 1] == 5 || (temp_array[count - 1] == 3 && temp_array[count - 2] == 7) || temp_array[count - 1] == 6) { return true; } } else { return false; } }

Credit Card Validity Identifier