堆排序

视频链接：https://www.bilibili.com/video/av47196993?from=search&seid=12418703498405255943

参考代码：

#include <iostream>
#include <algorithm>
//堆heap：1，完全二叉树；2，父节点的值大于子节点得值
//parent=(i-1)/2;
//c1=2*i+1;c2=2*i+2;
using namespace std;

void heapify(int tree[], int n, int i)//树，数的节点，当前节点
{
	if (i >= n)
		return;
	int c1 = 2 * i + 1;
	int c2 = 2 * i + 2;
	int max = i;
	if (c1<n && tree[c1] > tree[max])
		max = c1;
	if (c2<n && tree[c2] > tree[max])
		max = c2;
	if (max != i)
	{
		swap(tree[max],tree[i]);
		heapify(tree, n, max);
	}
}
void build_heap(int tree[], int n) //构建堆
{
	int last_node = n - 1;
	int parent = (last_node - 1) / 2;
	for (int i = parent; i >= 0; i--)
	{
		heapify(tree, n, i);
	}
}
void heap_sort(int tree[], int n)
{
	build_heap(tree, n);
	for (int i = n - 1; i >= 0; i--)
	{
		swap(tree[i],tree[0]);
		heapify(tree, i, 0);
	}
}
int main()
{
	int tree[] = { 4,10,3,5,1,2 };
	int n = 6;
	heap_sort(tree, n);
	for (int i = 0; i < n; i++)
		cout << tree[i] << " ";
	return 0;
}