基于堆的优先队列和用优先队列排序的例子

#include <stdio.h>

void exch(int& a, int &b)
{
    int tmp = a;
    a = b;
    b = tmp;
}

void fixup(int a[], int k)
{
    while(k>1 && a[k/2]<a[k])
    {
        exch(a[k/2], a[k]);
        k/=2;
    }
}

void fixdown(int a[], int k, int N)
{
    while(2*k <= N)
    {
        int j=k*2;
        if(j<N && a[j]<a[j+1]) j++;
        if(!(a[k]<a[j])) break;
        exch(a[k], a[j]);
        k = j;
    }
}

class PQ
{
    private:
        int *pq;
        int N;
    public:
        PQ(int maxN)
        {
            pq = new int[maxN+1];
            N = 0;
        }

        int empty() const
        {
            return N == 0;
        }

        void insert(int item)
        {
            pq[++N] = item;
            fixup(pq, N);
        }

        int getmax()
        {
            exch(pq[1], pq[N]);
            fixdown(pq, 1, N-1);
            return pq[N--];
        }
};

 

#include <stdio.h>
#include "PQ.cpp"

using namespace std;

void pqsort(int a[], int l, int r)
{
    int k;
    PQ pq(r-l+1);
    for(k=l; k<=r; k++)
        pq.insert(a[k]);
    for(k=r; k>=l; k--)
        a[k] = pq.getmax();
}

int main()
{
    int a[10] = {3,5,4,8,6,9,6,5,4,1};
    pqsort(a, 0, 9);
    for(int i=0; i<10; i++)
        printf("%d ", a[i]);
    printf("\n");
    return 0;
}