Thread: making program for comparing strings.

I know there is a function for comparing string but i am making it to just improve my concepts.
error : 2 is coming as answer when i put same sting in both place.

Code:

#include<stdio.h>
main()
{
char str1[] = "hello" ;
char str2[]= "hello" ;
int q;
q = xstrcmp(str1,str2);
printf("%d",q);
}


int xstrcmp(char *s1,char *s2)
{
while( *s1 != '\0' || s2 != '\0')
 {
 if (*s1 != *s2)
 {
  break;
 }
 s1= s1+1;
 s2=s2+1;
 }
 if ( *s1 == '\0' && *s2 == '\0')
  return(0);
 else if(*s1 == '\0' && *s2 != '\0')
  return(1);
 else if(*s1 != '\0' && *s2 == '\0')
  return(2);
 else if(*s1 != *s2)
 return(3);
}

Code:

while( *s1 != '\0' || s2 != '\0')

One of these things is not like the other.

Thanx ..was a silly mistake .

The while loop could be simplified... while (*s1 && *s1 != *s2)

Yeah, but code clarity is more important in my opinion (If it's to be shared with others anyways).

Originally Posted by Syscal

Yeah, but code clarity is more important in my opinion (If it's to be shared with others anyways).

Interesting. I'd have thought the simplified condition was clearer, but *shrug* I'll put the break back

Code:

int xstrcmp(const char *s1, const char *s2)
{
    unsigned char c1, c2;
    
    do {
        c1 = *s1++;
        c2 = *s2++;
        if (c1 == '\0')
            break;
    } while (c1 == c2);

    return c1 - c2;
}