【LeetCode】28

Implement strStr().

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

Solution: 

class Solution {
public:
    int strStr(string haystack, string needle) {    //runtime:4ms
        int len1=haystack.size(), len2=needle.size();
        for(int i=0;i<=len1-len2;i++)
        {
            int j=0;
            for(;j<len2;j++){
                if(haystack[i+j]!=needle[j])break;
            }
            if(j==len2)return i;
        }
        return -1;
    }
};