text: class Solution {
  public:
      vector<int> singleNumbers(vector<int>& nums) {
          unordered_set<int> a;
          for(auto &i : nums) {
  			auto t = a.find(i);
  			if(t == a.end()) a.insert(i);
  			else a.erase(t);
  		}
          return vector<int>(a.begin(), a.end());
      }
  };