28. Implement strStr()

Implement strStr().

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

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

class Solution {
public:
    int strStr(string haystack, string needle) {
        return haystack.find(needle);
        
    }
};