题目链接：模拟堆

#include <iostream>
#include <string.h>

using namespace std;

const int N = 100010;

int h[N], ph[N], hp[N], Size;

void heap_swap(int a, int b)
{
    swap(ph[hp[a]], ph[hp[b]]);
    swap(hp[a], hp[b]);
    swap(h[a], h[b]);
}

void down(int u)
{
    int t = u;
    if(u * 2 <= Size && h[u * 2] < h[t]) t = u * 2;
    if(u * 2 + 1 <= Size && h[u * 2 + 1] < h[t]) t = u * 2 + 1;
    if(u != t)
    {
        heap_swap(u, t);
        down(t);
    }
}

void up(int u)
{
    while(u / 2 && h[u / 2] > h[u])
    {
        heap_swap(u, u / 2);
        u >>= 1;
    }
}

int main()
{
    int n, m = 0;
    scanf("%d", &n);
    while(n--)
    {
        char op[10];
        scanf("%s", op);
        int k, x;
        if(!strcmp(op, "I"))
        {
            scanf("%d", &x);
            m++;
            Size++;
            h[Size] = x;
            ph[m] = Size, hp[Size] = m;
            up(Size);
        }
        else if(!strcmp(op, "PM"))
        {
            printf("%d\n", h[1]);
        }
        else if(!strcmp(op, "DM"))
        {
            heap_swap(1, Size);
            Size --;
            down(1);
        }
        else if(!strcmp(op, "D"))
        {
            scanf("%d", &k);
            k = ph[k];
            heap_swap(k, Size);
            Size --;
            down(k);
            up(k);
        }
        else 
        {
            scanf("%d%d", &k, &x);
            k = ph[k];
            h[k] = x;
            down(k);
            up(k);
        }
    }
    return 0;
}