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| #include <stdio.h>
enum CardType
{
type_master_card,
type_visa,
type_american_express,
type_other
};
static char* EmitentNames[] = {"Master Card", "VISA", "American Express", "Other"};
int GetFirstTwoDigits(const int* const cardNumber)
{
return (cardNumber[0] * 10 + cardNumber[1]);
}
enum CardType GetCardType(const int* const cardNumber)
{
enum CardType type;
int firstTwoDigits = GetFirstTwoDigits(cardNumber);
if ((firstTwoDigits >= 51) && (firstTwoDigits <= 55)) type = type_master_card;
else if (firstTwoDigits / 10 == 4) type = type_visa;
else if ((firstTwoDigits == 34) || (firstTwoDigits == 37)) type = type_american_express;
else type = type_other;
return type;
}
int Luhn(const int* const cardNumber, const int cardNumberLength)
{
int validationFlag = 0;
int p = 0;
int sum = 0;
int i = 0;
for (i = cardNumberLength - 1; i > -1; i--)
{
p = cardNumber[i];
if ((i + 1) % 2 == 0) p = p * 2;
if (p > 9) p = p - 9;
sum = sum + p;
}
if (sum % 10 == 0) validationFlag = 1;
return validationFlag;
}
void VerifyCard(const int* const cardNumber, const int cardNumberLength)
{
if (Luhn(cardNumber, cardNumberLength))
printf("This is a VALID credit card. Emitent: %s\n", EmitentNames[GetCardType(cardNumber)]);
else
printf("This card is INVALID!\n");
}
int main(void)
{
int card[] = {3, 7, 8, 7, 3, 4, 4, 9, 3, 6, 7, 1, 0, 0, 0};
VerifyCard(card, sizeof(card)/ sizeof(*card));
return 0;
} |
(
