[AcWing 839] 模拟堆

#include<iostream>

using namespace std;
const int N = 1e5 + 10;
int h[N], sz, m;
int ph[N], hp[N];
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 (2 * u <= sz && h[2 * u] < h[t]) t = 2 * u;
    if (2 * u + 1 <= sz && h[2 * u + 1] < h[t]) t = 2 * u + 1;
    if (t != u) {
        heap_swap(u, t);
        down(t);
    }
}
void up(int u)
{
    while (u / 2 && h[u / 2] > h[u]) {
        heap_swap(u / 2, u);
        u /= 2;
    }
}
int main()
{
    int n;
    cin >> n;
    while (n --) {
        string s;
        int k, x;
        cin >> s;
        if (s == "I") {
            cin >> x;
            sz ++;
            m ++;
            h[sz] = x;
            ph[m] = sz, hp[sz]= m;
            up(sz);
        }
        else if (s == "PM") cout << h[1] << endl;
        else if (s == "DM") {
            heap_swap(1, sz);
            sz --;
            down(1);
        }
        else if (s == "D") {
            cin >> k;
            k = ph[k];
            heap_swap(k, sz);
            sz --;
            down(k), up(k);
        }
        else if (s == "C") {
            cin >> k >> x;
            k = ph[k];
            h[k] = x;
            down(k), up(k);
        }
    }
    return 0;
}