1、B站视频链接：A15 堆 堆排序_哔哩哔哩_bilibili

题目链接：【模板】堆 - 洛谷

#include <iostream>
using namespace std;
int a[1000010],cnt;
void up(int u){ //上浮
  if(u/2 && a[u/2]>a[u]) 
    swap(a[u],a[u/2]), up(u/2);
}
void down(int u){ //下沉
  int v=u;
  if(u*2<=cnt && a[u*2]<a[v]) v=u*2;
  if(u*2+1<=cnt && a[u*2+1]<a[v]) v=u*2+1;
  if(u!=v) swap(a[u],a[v]), down(v);
}
void push(int x){ //压入
  a[++cnt]=x;
  up(cnt); 
}
void pop(){ //删除
  a[1]=a[cnt--];
  down(1);
}
int main(){
  int n; scanf("%d",&n); //操作次数
  while(n--){
    int op,x; scanf("%d",&op);
    if(op==1) scanf("%d",&x), push(x);
    else if(op==2) printf("%d\n",a[1]);
    else pop();
  }
  return 0;
}

2、STL大法好

#include <bits/stdc++.h>
using namespace std;
priority_queue<int,vector<int>,greater<int>> q;
//小根堆 
int main(){
	int n;
	cin>>n;
	while(n--){
		int op,x;
		cin>>op;
		if(op==1){
			cin>>x;
			q.push(x);
		}else if(op==2){
			cout<<q.top()<<endl;
		}else{
			q.pop();
		}
	}
	return 0;
}