优先队列模板

基础用法

int main() {
	/*
		c++优先队列默认为大根堆
	*/
	priority_queue<int, vector<int>> heap;
	heap.push(1);
	heap.push(2);
	heap.push(3);

	while(heap.size()){
		cout<<heap.top()<<' ';
		heap.pop();
	}
	/*output: 3 2 1*/


	/*
		优先队列设置为小根堆
	*/
	priority_queue<int, vector<int>, greater<int>> heap1;
	heap1.push(1);
	heap1.push(2);
	heap1.push(3);

	while(heap1.size()){
		cout<<heap1.top()<<' ';
		heap1.pop();
	}
	/*output: 1 2 3*/

	

	return 0;
	
}

利用仿函数自定义优先级比较

struct comparsion{
	bool operator () (PII A, PII B){
		if(A.first==B.first) return A.second>B.second;
		return A.first<B.first;
	}
};

int main(){
	/*
		自定义优先级进行比较
		typedef pair<int,int> PII;
		按照first从小到大排序，first相等时，按照second从大到小排序
	*/

	priority_queue<PII, vector<PII>, comparsion> heap;

	heap.push({2,3});
	heap.push({1,4});
	heap.push({2,1});
	heap.push({1,10});

	while(heap.size()){
		auto t= heap.top();
		heap.pop();
		cout<<t.first<<' '<<t.second<<endl;
	}
	/*
        与我们需要的刚好相反
		2 1
		2 3
		1 4
		1 10
	*/

	return 0;
}

修改自定义比较符号

struct comparsion{
	bool operator () (PII A, PII B){
		if(A.first==B.first) return -A.second>-B.second;
		return -A.first<-B.first;
	}
};

int main(){
	/*
		自定义优先级进行比较
		typedef pair<int,int> PII;
		按照first从小到大排序，first相等时，按照second从大到小排序
	*/

	priority_queue<PII, vector<PII>, comparsion> heap;

	heap.push({2,3});
	heap.push({1,4});
	heap.push({2,1});
	heap.push({1,10});

	while(heap.size()){
		auto t= heap.top();
		heap.pop();
		cout<<t.first<<' '<<t.second<<endl;
	}
	/*
		2 1
		2 3
		1 4
		1 10
	*/

	return 0;
}