## Problem

Implement strStr().

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

## Analysis

Brute force. Assume haystack has length n, and the needle has length m. We have

Time complexity: O(m*n)

## Solution

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