堆排序

#include<stdio.h>
void exchange(int *m,int *n)//交换
{
	int tem = *m;
	*m = *n;
	*n =tem;
}

void max_heap_adjust(int a[],int length,int i)//堆维护
{
	int l = 2*i+1;
	int r = 2*(i+1);
	int largest = i;
	if(l<= (length-1) && a[i]<a[l])
	{
		largest = l;
	}
	if(r<= (length-1) && a[largest]<a[r])
	{
		largest = r;
	}
	if( largest != i)
	{
		exchange(&a[largest],&a[i]);
		max_heap_adjust(a,length,largest);
	}

}

void build_max_heap(int a[],int length)//建堆
{
	for(int i=(length-1)/2;i>=0;i--)
	{
		max_heap_adjust(a,length,i);
	}



}

void heap_sort(int a[],int length)//堆排序
{
	int n = length;
	build_max_heap(a,length);
	
	for(int j=0;j<5;j++)
	{
		printf("%d... ",a[j]);
	}
	
	for(int i=length-1;i>=0;i--)
	{
		printf(" a[%d] = %d,a[0]= %d",i,a[i],a[0]);
		exchange(&a[i],&a[0]);//将堆首元素（最大的元素）依次交换到数组的后面去
		
	}
}

int main()
{
	int length = 5;
	int a[5]={5,3,17,10,84};
	heap_sort(a,5);
	printf(" \n");
	for(int i=0;i<5;i++)
	{
		printf("%d ",a[i]);
	}
	
	getchar();
	return 0;
}

堆排序主要工作都在建堆、堆维护，最后的排序阶段其实还是比较简单的。就好像是出栈。