AcWing 838. 堆排序

#include <bits/stdc++.h>
using namespace std;
const int N=1e6+10;
int h[N],num;
void down(int u){
    int t=u;
    if(u*2<=num&&h[u*2]<h[t]) t=u*2;
    if(u*2+1<=num&&h[u*2+1]<h[t]) t=u*2+1;
    if(u!=t){
        swap(h[u],h[t]);
        down(t);
    }
}
int main(){
    int n,m;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++) scanf("%d",&h[i]);
    num=n;
    for(int i=n/2;i>0;i--) down(i);
    while(m--){
        printf("%d ",h[1]);
        h[1]=h[num];
        num--;
        down(1);
    }

    return 0;
}