23-C01P12

C01P12 - Credit card validation

Implement a function, called is_credit_card_valid(number), which returns True or False based on the following algorithm:

1. Starting from the right, double every second digit.
2. If after doubling the digit becomes >= 10, calculate the sum of the digits of the new number & use that. For example, if we have 9 and doubling it gets us 18, the final result is going to be 1 + 8 = 9
3. After the transformation, we find the sum of all digits in the transformed number.
4. The number is valid, if the sum is divisible by 10.

This is also known as the Luhn algorithm.

For example: 79927398713 is valid, bacause:

1. After doubling, we get the following number:

                7 +
sum_digits(9 * 2) +
                9 +
sum_digits(2 * 2) +
                7 +
sum_digits(3 * 2) +
                9 +
sum_digits(8 * 2) +
                7 +
sum_digits(1 * 2) +
                3

2. And calculating the sum of the digits of the transformed number, we get 70 => the card number is valid.

Signature

def is_credit_card_valid(number):
    pass

Examples

is_credit_card_valid(79927398713) is True
is_credit_card_valid(79927398715) is False
is_credit_card_valid(4417123456789113) is True

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