A solution for cs50's credit card validation problem

credit card check

/**
  *
  * credit.c
  *
  * Peter Downs
  *
  * A program for validating credit card numbers.
  *
  */
  
#include <cs50.h>
#include <math.h>
#include <stdio.h>

int main(void)
{
    // Declare and initialize a variable and ask for user input.
    long long cardnumber = 0;
 
    // Ask for credit card number  

    do
    {printf("What is your card number? ");
    cardnumber = GetLongLong();
    }
    while (cardnumber < 0);

    // Determine whether it has a valid number of digits
    int count = 0;
    long long digits = cardnumber;
    while (digits > 0)
    {
        digits = digits/10;
        count++;
    }
    if ((count != 13) && (count != 15) && (count != 16))
    {
        printf("INVALID\n");
    }
    int number[count];
   
    
    for (int i = 0; i < count; i++)
    {
        number[i] = cardnumber % 10;
        cardnumber = cardnumber / 10;
    }
    
    int originalnumber[count];
    for (int i = 1; i < count; i++)
    {
        originalnumber[i] = number[i];
    }
    
    for (int i = 1; i < count; i+=2)
    {
        number[i] = number[i] * 2;
    }
    
    int v = 0;
    int temp;
    
    if (count == 13)
    {
      for (int i = 0; i < count; i++)
      {
        temp = (number[i] % 10) + (number[i]/10 % 10);
        v = v + temp;
      }
      if (originalnumber[12] == 4 && v % 10 == 0)
      {
        printf("VISA\n");
      }
      else
      {
        printf("INVALID\n");
      }
    }
    if (count == 15)
    {
      for (int i = 0; i < count; i++)
      {
        temp = (number[i] % 10) + (number[i]/10 % 10);
        v = v + temp;
      }
      if (originalnumber[14] == 3 && v % 10 == 0 && (originalnumber[13] == 4 || originalnumber[13] == 7))
      {
        printf("AMEX\n");
      }
      else
      {
        printf("INVALID\n");
      }
    }
    if (count == 16)
    {
      for (int i = 0; i < count; i++)
      {
        temp = (number[i] % 10) + (number[i]/10 % 10);
        v = v + temp;
      }
      if (originalnumber[15] == 4 && v % 10 == 0)
      {
        printf("VISA\n");
      }
      else if (originalnumber[15] == 5 && v % 10 == 0 && (originalnumber[14] == 1 || originalnumber[14] == 2 || originalnumber[14] == 3 || originalnumber[14] == 4 || originalnumber[14] == 5))
        {
            printf("MASTERCARD\n");
        }
      else
      {
        printf("INVALID\n");
      }
    }
  
    return 0;
}    

is there any way of implementation the logic without using arrays?

Yes check this
problem-1-solution without array

https://github.com/me50/DeHacker17/blob/cs50/problems/2020/x/credit/credit.c

trying to check how i can get you solution without using arrays but page not found.

You can check my solution
problem-1-solution without array

For those who are still beginners with arrays, they are cleverly introduced in the following week's lecture (CS50 Week 2):

https://www.youtube.com/watch?v=v7Ho89RMRIo&t=851

Above solutions will make much more sense after watching.

Mate, if you could leave any comments for your code that would be nice.

after line 42 they are needed so bad.