text: class Solution {
  public:
      vector<int> findDisappearedNumbers(vector<int>& nums) {
          vector<int> res;
          int len = nums.size();
          
          for (int i = 0; i < len; i++)
          {
              int tmp = abs(nums[i]) - 1;
              if (nums[tmp] > 0) nums[tmp] *= -1;
          }
      
          for (int i = 0; i < len; i ++)
              if (nums[i] > 0) res.push_back(i + 1);
          
          return res;
      }
  };