1 class Solution { 2 public: 3     string longestCommonPrefix(vector<string>& strs) { 4         string prefix=""; 5         if(strs.size()==0)  return prefix; 6  7         /** check char by char, for each char, check all the string word **/ 8         for(int k=0; k<strs[0].size(); k++){ 9             int i=1;10             for(; i<strs.size() && strs[i].size()>k; i++){11                 if(strs[i][k]!=strs[0][k])12                     return prefix;13             }14             if(i==strs.size()) prefix+=strs[0][k];15         }16         return prefix;17     }18 };