ansi_c_pg065_ch04_ex01.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>

#define	MAXLINE 1000		/* maximum input line length */


int get_line(char line[], int max);
int strindex(char source[], char searchfor[]);
char pattern[] = "ould";	/* pattern to search for */
/* find all lines matching pattern */

int
main()
{
	char line[MAXLINE];
	int found = 0;
	while (get_line(line, MAXLINE) > 0)
		if (strindex(line, pattern) >= 0) {
			printf("%s", line);
			found++;
		}
	return (found);
}

/* get_line:  get line into s, return length */
int
get_line(char s[], int lim)
{
	int c, i;
	i = 0;
	while (--lim > 0 && (c = getchar()) != EOF && c != '\n')
		s[i++] = c;
	if (c == '\n')
		s[i++] = c;
	s[i] = '\0';
	return (i);
}
/* strindex:  return index of t in s, -1 if none */
int
strindex(char s[], char t[])
{
	int i, j, k;
	i = strlen(s)  - 1;
	for (i = strlen(s)  - 1; i >= 0; i--) {
		for (j = i, k = 0; t[k] != '\0' && s[j] == t[k]; j++, k++)
			;

		if (k > 0 && t[k] == '\0')
				return (i);
	}
	return (-1);
}