14. Longest Common Prefix

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

class Solution {
public:
  string longestCommonPrefix(vector<string>& strs) {
    string res;
    int len = strs.size();
    if (len == 0){
      return res;
    }
    int i = 0;
    while (1){
      char base;
      if (strs[0].size() >= i + 1){
        base = strs[0][i];
      }
      else{
        break;
      }
      bool flag = false;
      for (int j = 1; j < len; j++){
        if (strs[j].size()>=i + 1 && strs[j][i] == base){
          continue;
        }
        else{
          flag = true;
          break;
        }
      }
      if (flag) break;
      res.push_back(base);
      i++;
    }
    return res;
  }
};