tcpl-ex-4-1.c

/*
 * Exercise 4-1. Write the function strindex(s,t) which returns the position 
 * of the rightmost occurrence of t in s, or -1 if there is none. 
 */
#include <stdio.h>
#include <string.h>

int strindex(char s[], char t[]);

int main(void)
{
	char* s[] = {"abcdefgabcdefg", "adefg"};
	char* t[] = {"def", "acg"};
	int r[] = {10, -1};
	size_t len = sizeof(s)/sizeof(s[0]);
	int i = 0;
	while (i < len)
	{
		if (r[i] == strindex(s[i], t[i]))
			printf("assert success.\n");
		else
			printf("assert fail.\n");
		i++;
	}
	return 0;
}

int strindex(char s[], char t[])
{
	int slen = strlen(s);
	int tlen = strlen(t);

	int i = slen - 1, j, k;

	while (i >= 0)
	{
		j = tlen - 1;
		k = i;
		while (k >= 0 && j >= 0 && s[k--] == t[j--])
			;
		if (j < 0)
			return k + 1;
		i--;
	}
	return -1;
}