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.

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>

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

#define MAXPATTERN 20

int getlin(char line[], int max);

int strindex(char source[], char searchfor[]);

char pattern[MAXPATTERN]; /*pattern to search for*/

/*find all line matching pattern*/

int main()

{

    char line[MAXLINE];

    int found, i;

    found = 0;

    

    printf("Enter the pattern: ");

    gets(pattern);

    while(getlin(line, MAXLINE) > 0)

        if((i = strindex(line, pattern)) >=0)

        {

            printf("%s", line);

            printf("the position of the rightmost occurence: %d\n", i);

            found++;

        }

        else 

            printf("occurence: %d\n", i);

    printf("%d\n", found);

    return 0;

}

/*getlin: get line into line[], return lenght*/

int getlin(char line[], int max)

{

    int c, i;

    

    i = 0;

    printf("Enter the line: ");

    while(--max > 0 && (c=getchar()) != EOF && c != '\n')

        line[i++] = c;

    if(c == '\n')

        line[i++] = c;

    line[i] = '\0';

    return i;

}

/*strindex: return index of pattern in line, -1 if none*/

int strindex(char source[], char searchfor[])

{

    int i, j, k, pos;

    

    for(pos = -1, i = 0; source[i] != '\0'; i++)

    {

        for(j = i, k = 0; searchfor[k] != '\0' && source[j] == searchfor[k]; j++, k++)

            ;

        if(k > 0 && searchfor[k] == '\0')

            pos = i;

    }

    return pos;

}

Result: