palindrome.c

palindrome.c

#include <stdio.h>
#include <string.h>

int is_palindrome(const char* text)
{
	/* Set the forward and backward iterators to outside
	   the string as they move in the first iteration. */
	const char* forward  = &text[0] - 1;
	const char* backward = &text[strlen(text)];
	
	/* Loop until the iterator has passed the middle,
	   or until the characters don't match. */
	while(!(forward > backward || *(++forward) != *(--backward)));
	
	/* If the middle has been passed, that means that all of the
	   characters up to (and including) the middle match.
	   Thus it's a palindrome. */
	return (forward >= backward);
}

int main(void)
{
	printf("racecar: %i\nnoimnot: %i\n",
		is_palindrome("racecar"),
		is_palindrome("noimnot"));
	
	return 0;
}

It reminds me of some old Programming Praxis at thedailywtf http://thedailywtf.com/Series/Bring_Your_Own_Code.aspx