/*
Program for
Written by: Alec
Wirrten on: Nov 2018
Written in: C
Compilied with: gcc
Version 7.2.1
*/

#include <stdio.h>

int main(void){
//Defines variables
int n1 = 0; //first 6 numbers
int n2 = 0; //2nd 6 numbers
int array1[6]; //number 1 array that contains 1st number set
int array2[6]; //second array containg numbers from n2
int count1 = 6; //sets array size later
int count2 = 6; //same

//Ask user to input data an reads it
printf("Enter the first 6 digits of the barcode: \n");
scanf("%i", &n1);
printf("Enter the first 6 digits of the barcode: \n");
scanf("%i", &n2);

//Splits number1 into individual digits
   count1 = 0;
   while (n1 > 0){
       array1[count1] = n1 % 10;
       n1 /= 10;
       count1++;
   }

   count2 = 0;
   while (n2 > 0){
       array2[count2] = n2 % 10;
       n2 /= 10;
       count2++;
   }
//Steps 1-3n
int sumo = array1[5]+array1[3]+array1[1]+array2[5]+array2[3]+array2[1]; //adds odd
int sume = array1[4]+array1[2]+array1[0]+array2[4]+array2[2]; //adds even without 12
int sumd = 3*sumo; //multiplies odds
int sum  = sume+sumd; //adds above and evens
int chec = sum%10;
int check = 10-chec;

//Step 4
if(chec == 0){ //Checks if last digit is 0
    if(chec == array2[0]){
        printf("The UPC is legal\n");
    }
    else{
        printf("The UPC is illegal\n");
    }
}
if(check == array2[0]){ //Sees if check digit is legal
    printf("The UPC is legal\n");
}
else{
    printf("The UPC is illegal\n");
}
printf("Digit 1 of array 1 is %i\n", array1[5]);
printf("Digit 1 of array 2 is %i\n", array2[5]);
return 0;
}