堆排序

#include "stdafx.h"

void MAX_HEAPIFY(int a[], int i, int len)
{
int l = 2 * i + 1, r = 2 * i + 2;
int largest = i;                                             //预设该节点为最大
if (l <= len &&a[l] > a[i])
{
largest = l;
}
if (r <= len &&a[r] > a[largest])
{
largest = r;
}
if (largest != i)
{
int temp = a[i];
a[i] = a[largest];
a[largest] = temp;
MAX_HEAPIFY(a, largest, len);
}
}

void BUILD_MAX_HEAO(int a[], int len)
{
for (int i = len / 2; i > -1; --i)
{
MAX_HEAPIFY(a, i, len);                                        //从下往上，保证每个都是最大堆
}
}

void HEAP_SORT(int a[],int len)
{
BUILD_MAX_HEAO(a,len);
int len2 = len;
for (int i = len; i > 0;--i)
{
int temp = a[0];
a[0] = a[i];
a[i] = temp;
--len2;                                                       //构建最大堆时排除最后一个节点
MAX_HEAPIFY(a, 0, len2);
}
}

int _tmain(int argc, _TCHAR* argv[])
{
int a[] = { 27, 17, 3, 16, 13, 10, 1, 5, 7, 12, 4, 8, 9, 0 };
int len = sizeof(a) / 4 - 1;
HEAP_SORT(a, len);
for (int i = 0; i < len + 1; ++i)
{
cout << a[i] << endl;
}
return 0;
}