credit cs50 solution
credit cs50 solution
xxxxxxxxxx#include <stdio.h>#include<cs50.h>#include <math.h>int main(void){long x = get_long("enter the credit card number");int digit = 0, sum = 0;//digit is used for odd and even checker.long y = x;//checksum card digitswhile (y != 0){ int sumeven = 0, sumodd = 0; int rem = y % 10; digit++; if (digit % 2 == 0) //if digit is even { int multiply = rem * 2; if (multiply == 0) { sumeven += multiply; } else { while (multiply != 0) //adding all digits after { sumeven += multiply % 10; multiply /= 10; //minus last digit of multiply } } } else //if digit is odd { sumodd += rem; } y /= 10; //minus last digit from y sum += sumeven + sumodd;}//check for valid credit cardif (digit != 13 && digit != 15 && digit != 16) //for first if{ printf("INVALID\n");}else if (sum % 10 == 0){ if (digit == 16) //if digit is 16 { if (x / 100000000000000 >= 51 && x / 100000000000000 <= 55) { printf("MASTERCARD\n"); } else if (x / 1000000000000000 == 4) { printf("VISA\n"); } else //if digit is not 16 { printf("INVALID\n"); } } else if (digit == 15) { if (x / 10000000000000 == 34 || x / 10000000000000 == 37) { printf("AMEX\n"); } else { printf("INVALID\n"); } } else if (digit == 13) { if (x / 1000000000000 == 4) { printf("VISA\n"); } else { printf("INVALID\n"); } }}else{ printf("INVALID\n");}}`Source: stackoverflow.com
Twitter 
LinkedIn