text: #include <bits/stdc++.h>
  using namespace std;
  class Solution {
     public:
      set<string> s;
      int n;
      string ans;
      void dfs(string cur) {
          if (ans.length()) return;
          if (cur.length() == n) {
              if (!s.count(cur)) ans = cur;
              return;
          }
          dfs(cur + '0');
          dfs(cur + '1');
      }
      string findDifferentBinaryString(vector<string>& nums) {
          n = nums[0].length();
          s = set<string>(nums.begin(), nums.end());
          dfs("");
          return ans;
      }
  };
  