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

If there is no common prefix, return an empty string "".

Example 1:

Input: ["flower","flow","flight"]Output: "fl"

Example 2:

Input: ["dog","racecar","car"]Output: ""Explanation: There is no common prefix among the input strings.

 

class Solution {public:    string longestCommonPrefix(vector
     
      & strs) {        int n = strs.size();        if(n == 0)            return "";        int k = 0;        string ans;        bool flag = true;        while(true) { // Kst char            if(strs[0].size() < k+1)                break;            char ch = strs[0][k];            for(int i=1; i