23王道大堆顶

#include<iostream>
using namespace std;

//a[0]空出来，辅助空间
int a[10] = { NULL,10,3,6,23,44,56,99,1,21 };

void HeadAdjust(int a[], int k, int len);
void buildMAXHeap(int a[], int len);
void swap(int& a, int& b);
void Headsort(int a[], int len);

//建立大根堆
void buildMAXHeap(int a[], int len) {
	//从最后一个非叶结点开始
	for (int i = len / 2; i >= 1; i--) {
		HeadAdjust(a, i, len);
	}
}

//调整以k为跟的子树
void HeadAdjust(int a[], int k, int len) {
	a[0] = a[k];//保存根节点
	for (int i = 2 * k; i <= len; i = 2 * i) {//左孩子为2i
		if (i < len && a[i] < a[i + 1])//找到大孩子下标
			i++;
		if (a[0] >= a[i]) break;//还是原来的根节点大
		else {
			a[k] = a[i];
			//a[i] = a[0];有break的情况，不能这么写
			k = i;
		}
		a[k] = a[0];
	}
	//a[k] = a[0];????
}

void swap(int& a, int& b) {
	int c = a;
	a = b;
	b = c;
}

void Headsort(int a[], int len) {
	buildMAXHeap(a, len);
	for (int i = len; i > 1; i--) {
		swap(a[1], a[i]);
		HeadAdjust(a, 1, i - 1);
	}
}

int main() {
	buildMAXHeap(a, 9);
	for (int i = 1; i < 10; i++)
		cout << a[i] << " ";
	cout << endl;
	//int x = 20, y = 30;
	//swap(x, y);
	//cout << x << endl;
	Headsort(a, 9);
	//这里传入的数是数组实际有多少个数字
	for (int i = 1; i < 10; i++)
		cout << a[i] << " ";
	return 0;
}