class Solution {

 public:

     string longestCommonPrefix(vector<string>& strs) {      //runtime:4ms

         string str="";

         if(strs.empty())return str;

         int index=;

         while(true){

             if(index>=strs[].size())return str;

             char c=strs[][index];

             for(int i=;i<strs.size();i++){

                 if(index>=strs[i].size()||strs[i][index]!=c)return str;

             }

             str+=c;

             index++;

         }

     }

 };