I am beginner a 1st year cs student. I am taking CS50 and I completed the first week problem of implementing Luhn Check algorithm. Though my solution works I feel it's very sloppy and not efficient. Can someone please suggest how can I improve my solution? (It's a first-week problem so you are not intended to use array or functions.)
Here is the code:
#include<stdlib.h>
#include<cs50.h>
int main()
{
long long x,j=0;
int len,i,len_flag,flag=0,flag_val=0,sp_len=0,check_flag=0; //basic integers related to loop etc
int res,sum,fin_sum=0,h=0,d2_sum=0,d1_sum=0,ff_num=0; // variables related to extracting numbers
int sum_len=0,in_sum=0,in_fsum=0,len_sum=0,m=0; // extraing numbers from more than single sum result
int sum_f=0,sum_final=0;
do{
x = get_long("enter a valid card number \n");
j=x;
len_flag = 0;
len = 0;
while(len_flag!=1)
{
x = x / 10;
if(x==0)
{
len_flag = 1; //finding the lenght of the number
}
len++;
}
if(len==15||len==16||len==13)
{
flag = 1;
sp_len =1;
}
else
{
flag=1;
}
}while(flag!=1);
for(i=0;i<len;i++)
{
res = j % 10;
j = j / 10;
if(i%2!=0)
{
sum = res * 2;
//printf("multi_res : %d \n",sum);
len_flag = 0;
sum_len = 0;
len_sum = sum;
while(len_flag!=1)
{
len_sum = len_sum / 10;
if(len_sum==0)
{
len_flag=1; // checking if the sum is more than single digit
}
sum_len++;
//printf("trig\n");
}
if(sum_len>1)
{ x=0;
while(x<sum_len)
{
in_sum = sum % 10;
sum = sum/10;
in_fsum = in_fsum + in_sum;
//printf("double sum : %d \n",in_fsum);
x++;
}
}
fin_sum = fin_sum + sum;
}
if(i==len-1)
{
for(h=0;h < 1;h++)
{
fin_sum = fin_sum + in_fsum;
}
d1_sum = res;
}
else if(i%2==0)
{
sum_f = sum_f + res; // adding up the number that where not x2
}
if(i==len-2)
{
d2_sum = res; //5555555555554444
}
}
sum_final = sum_f + fin_sum;
//printf("sum_final : %d\n",sum_final);
//printf("sum_f_final : %d\n",sum_f);
//printf("sum_in_final : %d\n",fin_sum);
if(sum_final%10==0)
{
flag_val=1; // checking if the number is valid
}
if(ff_num == 0)
{
ff_num = (d1_sum*10) + d2_sum; //flip
}
do
{
if(sp_len==0)
{
printf("INVALID\n");
check_flag=1;
break;
}
if((flag==1&&flag_val==1&&ff_num==34)||ff_num==37)
{
printf("AMEX\n");
check_flag=1;
break;
}
else if(flag==1&&flag_val==1&&ff_num>50&&ff_num<56)
{
printf("MASTERCARD\n");
check_flag=1;
break;
}
else if(flag==1&&flag_val==1&&d1_sum==4)
{
printf("VISA\n");
check_flag=1;
break;
}
else
{
printf("INVALID\n");
check_flag=1;
break;
}
}while(check_flag!=1);
return 0;
}
I felt like I was fixing a leak while writing the code. I would try to correct one thing and another thing would go wrong and this is the final result.
Thank you for your help. If the question was not asked properly please forgive me; it's my first time here.
"enter a valid card number \n"
which is an array. \$\endgroup\$ – chux - Reinstate Monica Apr 25 '20 at 9:03