堆排序

 

#include <iostream>

using std::cin;
using std::cout;

unsigned int GetLchild(unsigned int iPos)
{//注：堆排序中的树是完全2叉树,如果父亲节点是iPos那么左孩子是2 * iPos
	return 2 * iPos;
}

unsigned int GetRchild(unsigned int iPos)
{//注：堆排序中的树是完全2叉树,如果父亲节点是iPos那么右孩子是2 * iPos + 1
	return 2 * iPos + 1;
}

void Swap(int &a, int &b)
{//值交换
	int temp = a;
	a = b;
	b = temp;
}

void MaxHeapify(int * iArry, unsigned int iPos)
{//父亲节点和儿子节点比较和交换
	int iLchild = GetLchild(iPos);
	int iRchild = GetRchild(iPos);
	int iLargest = iPos;

	if (iLchild <= iArry[0] && iArry[iLchild] > iArry[iPos]) iLargest = iLchild;
	if (iRchild <= iArry[0] && iArry[iRchild] > iArry[iLargest]) iLargest = iRchild;
	if (iLargest != iPos){
		Swap(iArry[iLargest], iArry[iPos]);
		MaxHeapify(iArry, iLargest);//递归把原iPos的值放到合适的位置
	}
}

void BuildMaxHeap(int * iArry)
{//自底向上建立大顶堆
 //由于是完全2叉树,所以节点 n / 2 + 1到	n 的节点都是叶子节点
 //我们建堆得时候只需要从最后的节点n / 2开始到根节点调整即可
	for (unsigned int iPos = iArry[0] / 2; iPos != 0; --iPos){
		MaxHeapify(iArry, iPos);
	}
}

void HeapSort(int * iArry)
{//进行堆排序,每次把最后一个未排序的跟根节点(最大的)交换
 //实现从小到大排序

	BuildMaxHeap(iArry); //建立大顶堆

	for (unsigned int iPos = iArry[0]; iPos >= 1; --iPos){
		Swap(iArry[1], iArry[iPos]);
		iArry[0]--;
		MaxHeapify(iArry, 1);
	}
}

int main(void)
{
	unsigned int iLen;
	while (cin >> iLen){
	int * iArry = new int [iLen + 1];
	if (iLen == 0) return 0;
	iArry[0] = iLen;
	for (unsigned int i = 1; i <= iLen; ++i) cin >> iArry[i];

	HeapSort(iArry);

	for (unsigned int i = 1; i <= iLen; ++i) cout << iArry[i] << ' ';
	cout << '\n';
	delete []iArry;
	}
	return 0;
}