MinMaxPQ

need PriorityQueuePair.

template <typename T>
struct MinMaxPQ {
  PriorityQueuePair<T, std::greater<>> minq;
  PriorityQueuePair<T> maxq;

  [[nodiscard]] int size() const {
    return minq.size();
  }

  [[nodiscard]] bool empty() const {
    return size() == 0;
  }

  void insert(const T& x) {
    minq.insert(x);
    maxq.insert(x);
  }

  [[nodiscard]] const T& getMin() const {
    assert(!empty());
    return minq.get();
  }

  [[nodiscard]] const T& getMax() const {
    assert(!empty());
    return maxq.get();
  }

  void erase(const T& x) {
    minq.erase(x);
    maxq.erase(x);
  }
};