Write a function to find the longest common prefix string amongst an array of strings.

class Solution {

public:

    string longestCommonPrefix(vector<string> &strs) {

        // Start typing your C/C++ solution below

        // DO NOT write int main() function

        string result="";

        if(strs.size() == ) return result ;

        string first = strs[] ;

        for(int i = ; i < first.size() ;i++)

        {

           char c = first[i] ;

           for(int j = ; j< strs.size(); j++)

             if(i > strs[j].size() - ||  c != strs[j][i])

                 return result;

            result+=c;

        }

        return result ;

    }

};