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 swap(int &a, int &b)
{
    int t = a;
    a = b;
    b = t;
}

void max_heapify(int arr[],int size, int i)
{
    int l = left(i);
    int r = right(i);
    int largest = i;
    if(l<size && arr[l]>arr[largest])
        largest = l;
    if(r<size && arr[r] > arr[largest])
        largest = r;
    if(largest != i)
    {
        swap(arr[i], arr[largest]);
        max_heapify(arr,size,largest);
    }
}

void build_max_heap(int arr[],int size)
{
    int i = 0;
    for(i=size/2; i>=0; i--)
        max_heapify(arr,size,i);
}



void print_arr(int arr[], int size)
{
    for(int i=0; i<size; i++)
        cout<<arr[i]<<" ";
    cout<<endl;
}

void heapsort(int arr[], int size)
{
    cout<<"before heap sorting..."<<endl;
    print_arr(arr,size);
    int heap_size = size;
    build_max_heap(arr,size);
    for(int i=size-1; i>0; i--)
    {
        swap(arr[0],arr[i]);
        heap_size--;
        max_heapify(arr,heap_size,0);
    }
    cout<<"After heap sorting..."<<endl;
    print_arr(arr,size);
}


int main()
{
    int i = 0;
    int n;
    int arr[1000];
    cout<<"please input the size of array!"<<endl;
    cin>>n;
    cout<<"plead input the "<<n<<" numbers!"<<endl;

    for(i = 0; i<n; i++)
        cin>>arr[i];
    heapsort(arr,n);
    return 0;
}