ss.c

ss.c

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

int ss(char *n, char *h) {
    const size_t n_len = strlen(n);
    // empty needle is in haystack
    if (n_len == 0) return 1;
    const size_t h_len = strlen(h);
    // needle cannot be longer than haystack
    if (n_len > h_len) return 0; 
    // equal lengths must have equal values
    if (n_len == h_len) return (0 == strncmp(n,h,n_len));

    char *c = h;
    while (*c) {
        size_t c_l = strlen(c);
        // needle now bigger than substring
        if (c_l < n_len) return 0;
        // c has len at least n_len, try an n_len compare
        if (0 == strncmp(c,n,n_len)) return 1;
        c++;
    }
    return 0;
}

int main(void) {
    char *needle = "ays";
    char *haystack = "haystack";
    const int is_ss = ss(needle,haystack);
    printf("is needle '%s' in haystack '%s' ? %d\n",needle,haystack,is_ss);
    return 0;
}