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@joel29dec
Created June 30, 2019 20:36
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credit card validator in c
#include <math.h>
#include <stdio.h>
int main(void)
{
// Declare and initialize cardname variable.
// Change variable below to test credit card number
long long cardnumber = 378282246310005;
// Determine whether it has a valid number of digits
int count = 0;
long long digits = cardnumber;
//checks for card length of 13, 15, or 16
while (length > 0)
{
length = length/10;
count++;
}
if ((count != 13) && (count != 15) && (count != 16))
{
printf("INVALID\n");
}
// create array size with the count of the number
int number[count];
// store each digit of card number in the array number
for (int i = 0; i < count; i++)
{
number[i] = cardnumber % 10;
cardnumber = cardnumber / 10;
}
// number = [1,8,8,1,8,8,8,8,8,8,8,8,2,1,0,4]
int cardarray[count];
for (int i = 1; i < count; i++)
{
cardarray[i] = number[i];
}
// multiply every other number in the array
for (int i = 1; i < count; i+=2)
{
number[i] = number[i] * 2;
}
// cardarray = [8,8,1,8,8,8,8,8,8,8,8,2,1,0,4]
// number = [1,16,8,2,8,16,8,16,8,16,8,16,2,2,0,4]
int accumulator = 0;
int sumdigit;
if (count == 13)
{
for (int i = 0; i < count; i++)
{
sumdigit = (number[i] % 10) + (number[i]/10 % 10);
accumulator = accumulator + sumdigit;
}
if (cardarray[12] == 4 && accumulator % 10 == 0)
{
printf("VISA\n");
}
else
{
printf("INVALID\n");
}
}
if (count == 15)
{
for (int i = 0; i < count; i++)
{
sumdigit = (number[i] % 10) + (number[i]/10 % 10);
accumulator = accumulator + sumdigit;
}
if (cardarray[14] == 3 && accumulator % 10 == 0 && (cardarray[13] == 4 || cardarray[13] == 7))
{
printf("AMEX\n");
}
else
{
printf("INVALID\n");
}
}
if (count == 16)
{
for (int i = 0; i < count; i++)
{
sumdigit = (number[i] % 10) + (number[i]/10 % 10);
accumulator = accumulator + sumdigit;
}
if (cardarray[15] == 4 && accumulator % 10 == 0)
{
printf("VISA\n");
}
else if (cardarray[15] == 5 && accumulator % 10 == 0 && (cardarray[14] == 1 || cardarray[14] == 2 || cardarray[14] == 3 || cardarray[14] == 4 || cardarray[14] == 5))
{
printf("MASTERCARD\n");
}
else
{
printf("INVALID\n");
}
}
return 0;
}
@bfamzz
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bfamzz commented Apr 30, 2020

You did not initialize the variable "length"

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