Implement strStr()

Implement strStr()

Implement strStr().

Returns a pointer to the first occurrence of needle in haystack, or null if needle is not part of haystack.

The fastest Boyer-Moorer algorithm can be found here.

class Solution {
public:
    char *strStr(char *haystack, char *needle) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (!haystack || !needle) return NULL;
        if (!*needle) return haystack;
        string const text(haystack);
        string const pattern(needle);
        size_t const pMax = pattern.size() - 1;
        for(size_t tailPos = pMax; tailPos < text.size();){
            size_t tPos = tailPos;
            int pPos = pMax;
            for(; pPos >= 0; --pPos, --tPos){
                if (text[tPos] != pattern[pPos]){
                    ++tailPos;
                    break;
                }
            }//for pPos
            if (pPos < 0) return (haystack + tailPos - pMax);
        }//for tPos
        return NULL;
    }
};