28. Implement strStr() (C++)

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) {
        if(needle.length()==0) return 0;
        int len=haystack.length()-needle.length();
        for(int i=0;i<len+1;i++){
            int j=0;
            for(;j<needle.length();j++){
                if(haystack[i+j]!=needle[j]){
                    break;
                }
            }
            if(j==needle.length()){
                return i;
            }
        }
        return -1;
    }
};