vector<vector<int>> threeSum(vector<int> &nums) {
  vector<vector<int>> sums;
  unordered_map<int, vector<int>> allnums;
  for (int i = 0; i < nums.size(); i++) {
    auto t = allnums.find(nums[i]);
    if (t == allnums.end()) {
      allnums.emplace(make_pair(nums[i], vector<int>{i}));
    } else {
      t->second.emplace_back(i);
    }
  }

  for (int i = 0; i < nums.size(); i++) {
    for (int j = 0; j < nums.size(); j++) {
      if (i == j) {
        continue;
      }
      auto sum = nums[i] + nums[j];
      auto t = allnums.find(0 - sum);
      if (t == allnums.end()) {
        continue;
      }
      int flag = 0;
      for (auto &ind : t->second) {
        if (ind != i && ind != j) {
          flag = 1;
        }
      }
      if (flag) {
        auto a = vector<int>{nums[i], nums[j], t->first};
        sort(a.begin(), a.end());
        if (find(sums.begin(), sums.end(), a) == sums.end()) {
          sums.emplace_back(a);
        }
      }
    }
  }
  return sums;
}