堆排序

#include<iostream>
using namespace std;

void maxHeapfy(int a[], int i, int heapsize)
{//大顶堆
    int left=2*i+1, right=2*i+2;
    int largest=i;
    //注意都是和a[largest]比较！！！
    if(left<heapsize && a[left]>a[largest])
        largest=left;
    if(right<heapsize && a[right]>a[largest])
        largest=right;
    if(largest != i){
        swap(a[i], a[largest]);
        maxHeapfy(a, largest, heapsize);//追踪下移节点
    }
}
void buildHeap(int a[], int n)
{
    for(int i=n/2-1;i>=0;i--){
        maxHeapfy(a, i, n);
    }
}
void heapSort(int a[], int n)
{
    buildHeap(a, n);
    int heapsize=n;
    while(heapsize>1){//堆里元素多于一个时
        swap(a[0], a[heapsize-1]);//将堆顶和最后一个元素交换
        heapsize--;//堆大小减一
        maxHeapfy(a,0,heapsize);//将剩下元素重新调整堆
    }
}
int main()
{
     int a[]={8,3,6,10,55,7};
     int n=sizeof(a)/sizeof(a[0]);
     heapSort(a, n);
     for(int i=0;i<n;i++)
        cout<<a[i]<<" ";
     cout<<endl;
     return 0;
}