HDU 1280 第M大数 堆的应用

#include <iostream>
#include<cstdlib>
#include<cstdio>
using namespace std;
int N;
int M;
int sequence[3000];
int order[3000];
class Minheap
{
private:
    int* heap;
    int currentSize;
    int MaxHeapSize;
    void FilterDown(int start,int endOfheap)
    {
        int i=start;
        int j=2*i+1;
        int temp=heap[i];
        while(j<=endOfheap)
        {
            if(j<endOfheap && heap[j]>heap[j+1])j++;
            if(temp<=heap[j])break;
            else
            {
                heap[i]=heap[j];
                i=j;
                j=2*j+1;
            }
        }
        heap[i]=temp;
    }
    void FilterUp(int start)
    {
        int j=start;
        int i=(start-1)>>1;
        int temp=heap[j];
        while(i>=0)
        {
            if(heap[i]<=temp)break;
            else
            {
                heap[j]=heap[i];
                j=i;
                i=(i-1)>>1;
            }
        }
        heap[j]=temp;
    }

public:
    Minheap()
    {
        currentSize=0;
        this->MaxHeapSize=M;
        heap=new int[M];
    }
    void insert(int x)
    {
        heap[currentSize]=x;
        FilterUp(currentSize);
        currentSize++;
    }
    int top(){return heap[0];}
    int Remove()
    {
        int Min=heap[0];
        heap[0]=heap[currentSize-1];
        currentSize--;
        FilterDown(0,currentSize-1);
        return Min;
    }
    void modify(int x)
    {
        heap[0]=x;
        FilterDown(0,currentSize-1);
    }
    ~Minheap(){delete heap;}
};
int main()
{
    while(scanf("%d %d",&N,&M)!=EOF)
    {
        int i,j,k;
        Minheap * heap=new Minheap();
        for(i=1;i<=M;i++)
        {
            heap->insert(0);
        }
        for(i=0;i<N;i++)
        {
            scanf("%d",&sequence[i]);
        }
        for(i=0;i<N;i++)
        {
            for(j=i+1;j<N;j++)
            {
                if((sequence[i]+sequence[j])>heap->top())
                {
                    heap->modify(sequence[i]+sequence[j]);
                }
            }
        }
        for(i=M-1;i>=0;i--)
        {
            order[i]=heap->Remove();
        }
        for(i=0;i<M-1;i++)
        {
            printf("%d ",order[i]);
        }
        printf("%d\n",order[i]);
    }
}