大根堆

#include <iostream>

using namespace std;

const int maxn = 100;
int a[maxn],n,heapsize;

void maxheapify(int i)     //根据数组的下表对应节点，对其左右两个子节点进行堆构造；
{
      int l,r,largest,t;
      l = i<<1;
      r = (i<<1)+1;
      if(l<=heapsize && a[i]<a[l])
            largest = l;
      else
            largest = i;
      if(r<=heapsize && a[r]>a[largest])
            largest = r;
      if(largest!=i)
      {
            t = a[i];
            a[i] = a[largest];
            a[largest] = t;
            maxheapify(largest);
      }
      return;
}

void BuildMaxHeap()    //建堆
{
      heapsize = n; //用在heapsort函数中，记录一下n的值；
      for(int i = n/2;i >= 1; i--)
            maxheapify(i);
      return;      
}

void heapsort()
{
      int i,t;
      BuildMaxHeap();
      for(i = n;i >= 2;i--)
      {
            t = a[1];
            a[1] = a[i];
            a[i] = t;
            heapsize--;
            maxheapify(1);
      }
}

int main()
{
      int i;
      cin >> n;
      for(i = 1; i <= n;i++)
            cin >>a[i];
            
      heapsort();  //建堆主函数
      
      for(i = 1;i <= n;i++)
      {
            cout << a[i] << endl;
      }
    return 0;
}