PQ 두 개로 최소/최대만 필요한 set 대체하기

heap_set.cpp

template<class T=int, class O=less<T>>
struct heap_set {
	priority_queue<T, vector<T>, O> q, del;
	const T& top() const { return q.top(); }
	int size() const { return int(q.size()-del.size()); }
	bool empty() const { return !size(); }
	void flush() { while(del.size() && q.top()==del.top()) q.pop(), del.pop(); }
	void insert(const T x) { q.push(x); flush(); }
	void pop() { q.pop(); flush(); }
	void erase(const T x) { del.push(x); flush(); }
};