堆排序-c++

/*************************************************************************
    > File Name: HeapSort.cpp
    > Author: zhoukang
    > Mail: zhoukang199191@126.com 
    > Created Time: 2014年08月11日 星期一 22时36分38秒
 ************************************************************************/

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

void max_heapfy(vector<int> & A,int index,int heapsize)
{
    int l = 2*index+1;
    int r = 2*index+2;

    int largest = index;
    if(l <= heapsize && A[l] > A[index])
        largest = l;
    if(r <= heapsize && A[r] > A[largest])
        largest = r;
    if(largest != index)
    {
        swap(A[index],A[largest]);
        max_heapfy(A,largest,heapsize);
    }
}

void build_max_heap(vector<int> &A,int heapsize)
{
//    assert(heapsize >= 0);
    int i;
    for(i = heapsize/2-1 ; i >= 0 ; --i)
        max_heapfy(A,i,heapsize);
}

void heap_sort(vector<int> &A,int heapsize)
{
    build_max_heap(A,heapsize);
    int i;
    for(i = heapsize-1; i > 0 ; --i )
    {
        swap(A[0],A[i]);
        max_heapfy(A,0,i);
    }
}

int main()
{
    cout<<"before"<<endl;
    vector<int> A;
    A.push_back(3);
    A.push_back(1);
    A.push_back(2);
    heap_sort(A,3);
}