堆排序

#include <iostream>
using namespace std;

int parent(int i)
{
    return i/2;
}

int left(int i)
{
    return 2*i;
}

int right(int i)
{
    return 2*i+1;
}

void exchange(int &a,int &b)
{
    int temp;
    temp=a;
    a=b;
    b=temp;
}

void max_heapify(int *a,int i,int heap_size)
{
    int l=left(i);
    int r=right(i);
    int largest;
    if (l<=heap_size&&a[l]>a[i])
    {
        largest=l;
    }
    else
    {
        largest=i;
    }
    if (r<=heap_size&&a[r]>a[largest])
    {
        largest=r;
    }
    if (largest!=i)
    {
        exchange(a[i],a[largest]);
        max_heapify(a,largest,heap_size);
    }

}

void build_max_heap(int *a,int heap_size)
{
    for (int i=heap_size/2;i>=0;i--)
    {
        max_heapify(a,i,heap_size);
    }
}

void heapsort(int *a,int heap_size)
{
    build_max_heap(a,heap_size);
    int length;
    length=heap_size;
    for (int i=length;i>=1;i--)
    {
        exchange(a[0],a[i]);
        heap_size=heap_size-1;
        max_heapify(a,0,heap_size);
    }
}

int main()
{
    int a[]={4,1,3,2,16,9,10,14,8,7,3,2,45,7,86,4,3,2,1};
    int heap_size=sizeof(a)/sizeof(int)-1;
    heapsort(a,heap_size);

    for (int i=0;i<=heap_size;i++)
    {
        cout<<a[i]<<"";
    }
    cout<<endl;
    system("pause");
    return 0;

}