就硬暴力，暴力中的暴力，匹配到对不上的直接从这次匹配到的开头下标+1重匹。

class Solution {
public:int strStr(string haystack, string needle){if (needle.empty()){return 0;}int j = 0, i = 0;while (j < needle.size() && i < haystack.size()){if (haystack[i] != needle[j]){if (j != 0){i -= j;}j = 0;}else{j++;}i++;}if (j == needle.size()){return i - needle.size();}return -1;}
};