int compstring(const char *string1, const char *string2)
{
int size1 = strlen(string1);
int size2 = strlen(string2);
for(int index = 0; string1[index] != ''\0'' && string2[index] != ''\0'' && index < size1 && index < size2; index++)
{
if(string1[index] == string2[index])
{
continue;
}
else
{
return 0;
}
}
return 1;
}
What's wrong with this?
March 05, 2002 09:32 PM
I whipped this string comparison function up in under a minute and it compiled, first try!
So there must be SOMETHING wrong with it.
IE it''s not portable or there''s uneeded stuff in it, etc.
So, how can I make it better?
March 05, 2002 09:36 PM
Ok, so I didn''t need the strlen() stuff, since the ''\0'' condition takes care of that... So now I have
How''s this look?
int compstring(const char *string1, const char *string2){ for(int index = 0; string1[index] != ''\0'' && string2[index] != ''\0''; index++) { if(string1[index] == string2[index]) { continue; } else { return 0; } } return 1;} How''s this look?
March 05, 2002 09:39 PM
Even better...
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int compstring(const char *string1, const char *string2){ int limit = (strlen(string1)> strlen(string2)) ? strlen(string2) : strlen(string1); for(int index = 0; index < limit; index++) if(!(string1[index] == string2[index])) return 0; return 1;} //email me.//zealouselixir software.//msdn.//n00biez.//
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1,788
March 05, 2002 09:41 PM
If you cut out the strlens, you need a final test to make sure the sizes are equal.
Edited by - sneftel on March 5, 2002 10:42:55 PM
int compstring(const char *string1, const char *string2){ for(int index = 0; string1[index] != '\0' && string2[index] != '\0'; index++) { if(string1[index] == string2[index]) { continue; } else { return 0; } } return (string1[index] == string2[index] ? 1 : 0);} Edited by - sneftel on March 5, 2002 10:42:55 PM
1,788
March 05, 2002 09:44 PM
quote: Original post by ZealousElixir
Even better...
int compstring(const char *string1, const char *string2){ int limit = (strlen(string1)> strlen(string2)) ? strlen(string2) : strlen(string1); for(int index = 0; index < limit; index++) if(!(string1[index] == string2[index])) return 0; return 1;} Ew... three calls to strlen. Don''t forget to consider the performance of standard functions; they tend to be very well optimized, but strlen will never go under best-case of O(n).
122
March 05, 2002 09:49 PM
If you want to make sure the strings are the same length you could possibly speed it up with the following.
Edit: Spelling and code errors.
Edited by - slepyii on March 5, 2002 10:51:02 PM
int compstring(const char *string1, const char *string2){ int str1len, str2len; str1len = strlen(string1); str2len = strlen(string2); if (str1len != str2len) return 0; for(int index = 0; index < str1len; index++) { if(string1[index] == string2[index]) { continue; } else { return 0; } } return 1;} Edit: Spelling and code errors.
Edited by - slepyii on March 5, 2002 10:51:02 PM
1,788
March 05, 2002 09:51 PM
quote: Original post by slepyii
If you want to make sure the strings are the same length you could possible speed it up with the following.
int compstring(const char *string1, const char *string2){ int str1len, str2len; str1len = str1len(string1); str2len = str2len(string2); if (str1len != str2len) return 0; for(int index = 0; index < str1len; index++) { if(string1[index] == string2[index]) { continue; } else { return 0; } } return 1;} Again.... don''t assume strlen is magic. Each of those calls iterates through the entire string, a character at a time, looking for a null. Since you''re going to be iterating through yourself anyway, you may as well stop before you iterate all the way through.
March 05, 2002 10:06 PM
I included the string length comparison condition, but I needed to alter it.
This is because when I call the function compstring(command, "stats"); "stats" doesn''t have a nul character, while command does, since it was aquired using fgets()... Or something like that.
I dunno
int str1len, str2len; str1len = strlen(string1); str2len = (strlen(string2)) + 1; if (str1len != str2len) { return 0; } This is because when I call the function compstring(command, "stats"); "stats" doesn''t have a nul character, while command does, since it was aquired using fgets()... Or something like that.
I dunno
March 05, 2002 10:19 PM
Oooo, ouch!
I just realized, I''d better tack a nul character onto that string, lest it renders my comparison condition useless.
I just realized, I''d better tack a nul character onto that string, lest it renders my comparison condition useless.
March 05, 2002 10:33 PM
quote: Original post by Sneftel
Ew... three calls to strlen. Don''t forget to consider the performance of standard functions; they tend to be very well optimized, but strlen will never go under best-case of O(n).
3 calls to strlen vs. 2 calls to strlen and two temp variables?
Maybe if you wanted to go all out, but the performance gain with strings of reasonable size is negligible, and the other code is a lot prettier. Also, if you''re using the methods that don''t require strlen at all, you''re doing three comparisons per loop iteration...a bit excessive.
Later,
ZE.
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