28 Implement strStr()

Implement strStr().
Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Brute-Force Solution

class Solution {
public:
    int strStr(string haystack, string needle) {
        int h = haystack.size(), n = needle.size();
        if ( n > h ) return -1;
        if ( n == 0 ) return 0;
        int ih = 0, in;
        while ( ih <= h - n + 1) {
            in = 0;
            while ( in <= n-1 ) {
                if ( haystack[ih+in] != needle[in] ) break;
                else in += 1;
            }
            if ( in == n ) return ih;
            ih += 1;
        }
        return -1;
    }
};