added checks 8, 9, and 10

cs50 / checks

Checks for check50

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Closed BenjaminDoran closed 6 years ago

BenjaminDoran commented 7 years ago

To confirm student is checking length of number and both the first and second digits on AMEX and MASTERCARD

Previously students were able to get a 5 on correctness by implementing checksum and confirming first digit matched the credit card provider.

dmalan commented 6 years ago

@brianyu28 afraid this one is still open. Mind taking a look? Sorry, @BenjaminDoran! CC @curiouskiwi