1 /*
2  * Exercise 4-1. Write the function strrindex(s,t), which returns the position
3  * of the rightmost occurrence of t in s, or -1 if there is none.
4  */
5 
6 #include <stdio.h>
7 #include <string.h>
8 #define MAXLINE 1000 /* maximum input line length */
9 
10 int getlin(char line[], int max);
11 int strindex(char source[], char searchfor[]);
12 int strrindex(char s[], char t[]);
13 
14 char pattern[] = "or"; /* pattern to search for */
15 
16 /* find all lines matching pattern */
17 
18 int main() {
19 	char line[MAXLINE];
20 	int found = 0;
21 	int index = 0;
22 
23 	printf("pattern: %s\n", pattern);
24 	while (getlin(line, MAXLINE) > 0)
25 		if ((index = strrindex(line, pattern)) >= 0) {
26 			printf("index: %d, %s", index, line);
27 			found++;
28 	}
29 	return found;
30 }
31 
32 /* getlin: get line into s, return length */
33 int getlin(char s[], int lim) {
34 	int c, i;
35 	i = 0;
36 	while (--lim > 0 && (c=getchar()) != EOF && c != '\n')
37 		s[i++] = c;
38 	if (c == '\n')
39 		s[i++] = c;
40 	s[i] = '\0';
41 	return i;
42 }
43 
44 /* strindex: return index of t in s, -1 if none */
45 int strindex(char s[], char t[]) {
46 	int i, j, k;
47 	
48 	for (i = 0; s[i] != '\0'; i++) {
49 		for (j=i, k=0; t[k] != '\0' && s[j] == t[k]; j++, k++)
50 			;
51 		if (k > 0 && t[k] == '\0')
52 			return i;
53 	}
54 	return -1;
55 }
56 
57 /* strrindex: return index of rightmost t in s, -1 if none */
58 int strrindex(char s[], char t[]) {
59 	int i, j, k;
60 	for (i = strlen(s)-1; s[i] != '\0'; i--) {
61 		for (j=i, k=0; t[k] != '\0' && s[j] == t[k]; j++, k++)
62 			;
63 		if (k > 0 && t[k] == '\0')
64 			return i;
65 	}
66 	return -1;
67 }