c++学习之--排序5-堆排序

<pre code_snippet_id="76498" snippet_file_name="blog_20131121_1_2374128" name="code" class="cpp"><pre code_snippet_id="76498" snippet_file_name="blog_20131121_1_2374128" name="code" class="cpp">

#include <iostream>

using namespace std;

// 58 45 72 86 77 21 34 60

void Swap(int *x,int *y)
{
int t;
t=*x;
*x=*y;
*y=t;
}

void HeapAdjust(int *a,int i,int size)
{
int lchild=2*i;
int rchild=2*i+1;
int max=i;
if(i<=size/2)
{
if(lchild<=size && a[lchild]>a[max])
{
max=lchild;
}
if(rchild<=size && a[rchild]>a[max])
{
max=rchild;
}
if(max!=i)
{
Swap(&a[i],&a[max]);
HeapAdjust(a,max,size);
}
}
}

void BuildHeap(int *a,int size)
{
int i;
for(i=size/2;i>=1;i--)
{
HeapAdjust(a,i,size);
}
}

void HeapSort(int *a,int size)
{
BuildHeap(a,size);
for(int i=size;i>=1;i--)
{
Swap(&a[1],&a[i]);
HeapAdjust(a,1,i-1);
}
}

int main()
{
int n,i;
cin>>n;
int *a=new int[n+1];
for(i=1;i<=n;i++)
{
cin>>a[i];
}

HeapSort(a,n);

for(i=1;i<=n;i++)
{
cout<<a[i]<<" ";
}
cout<<endl;
return 0;
}

//堆排序 (大顶堆)
//不稳定，建堆需要时间较长 时间复杂度为 O(n*log2(n))