关于堆排序

#include<iostream>
#include<cstdio>
using namespace std;
long long n,a[10000000];
void heapify(long long num,long long id)//维护大根堆堆性质,复杂度LogN 
{
	long long greatest=id,lson,rson;
	lson=id*2+1;
	rson=id*2+2;
	if(lson<num&&a[lson]>a[id])greatest=lson;
	if(rson<num&&a[rson]>a[id])greatest=rson;
	if(greatest!=id)
	{
		swap(a[id],a[greatest]);
		heapify(num,greatest);
	}
 } 
void heap_sort()
{
	for(long long i=n/2-1;i>=0;i--)
	heapify(n,i);//建堆
	//排序
	for(long long i=n-1;i>=0;i--)
	{
		swap(a[0],a[i]);
		heapify(i,0);
	 } 
}
int main()
{
	scanf("%lld",&n);
	for(long long i=0;i<=n-1;i++)
	scanf("%lld",&a[i]);
	heap_sort();
	for(long long i=0;i<=n-1;i++)
	printf("%lld ",a[i]);
}