![]() ![]() ![]() and every other odd digit in the reversed digits and sum them to form the partial sum. Sum the digits 7+2+5+3+2+2+6+2+5+3+1+2+0+5+3+9 = 57ĥ7 is not evenly divisible by 10, so this number is not valid. Reverse the order of the digits in the number. ![]() This number is valid! Example 2: invalid credit card number 8273 1232 7352 0569ĭouble the second digits, starting from the right 7253 2262 5312 0539 If the sum is evenly divisible by 10, then the number is valid. If doubling the number results in a number greater than 9 then subtract 9 from the product. The first step of the Luhn algorithm is to double every second digit, starting from the right. Example 1: valid credit card number 4539 3195 0343 6467 Goal: To write a program in C that can validate credit card numbers using the Luhn Algorithm, and return whether a valid card number is Mastercard, Visa or Amex.The program must ask for the number. Spaces are allowed in the input, but they should be stripped before checking.Īll other non-digit characters are disallowed. Strings of length 1 or less are not valid. The task is to check if a given string is valid. The Luhn algorithm is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers and Canadian Social Insurance Numbers. Given a number determine whether or not it is valid per the Luhn formula. ![]()
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