leetcode-28-implement strStr()

class Solution {
public:
    int strStr(string haystack, string needle) {
        if(needle == "")
            return 0;
        int lenHay = haystack.size();
        int lenNee = needle.size();
        for(int i=0;i<lenHay;i++){
            if(haystack[i] == needle[0]){
                for(int j=i; j<i+lenNee;j++){
                    if(haystack[j] == needle[j-i]){
                        if(j-i == lenNee-1)
                            return i;
                    }
                    else
                        break;
                }
            }
        }
        return -1;
    }
};

速度奇慢，后期改进。