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

#define STRING "test string with lost of stuff"

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

/* pass optional searchfor arg to strindex with STRING, pretty print result */
int main(int argc, char *argv[])
{
    char s[] = STRING; 
    char *t = (argc > 1) ? argv[1] : "est";
    
    int i = strindex(s, t);
    if (i < 0) {
        printf("no match\n");
        return 1;
    }

    printf("%s\n", s);
    while (i--)
        putchar(' ');
    printf("^\n");
    return 0;
}

/* strindex: return index of the righmost occurence of t in s, -1 if none */
int strindex(char s[], char t[])
{
    int i, j;
    const int tlen = strlen(t);

    j = tlen - 1;
    for (i = strlen(s)-1; i; i--)
        if (s[i] != t[j])
            j = tlen - 1;
        else if (!(j--)) // match found
            return i;
    return -1;
}