洛谷 P3369 【模板】普通平衡树

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#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
using namespace std;
//Mystery_Sky
//平衡树模板 
#define M 1000100
#define INF 0x3f3f3f3f
#define ll long long
inline int read()
{
    int x=0, f=1; char c=getchar();
    while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();}
    while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();}
    return x*f;
}
int n;
int root, tot;
int son[M][2];
int val[M], dat[M], size[M], cnt[M]; 

inline int New(int x)
{
    val[++tot] = x;
    dat[tot] = rand();
    size[tot] = 1;
    cnt[tot] = 1;
    return tot;
}

inline void pushup(int id)
{
    size[id] = size[son[id][0]] + size[son[id][1]] + cnt[id];
}

inline void build()
{
    root = New(-INF);
    son[root][1] = New(INF);
    pushup(root);
}

void Rotate(int &id, int d)//旋转操作
{
    int k = son[id][d^1];
    son[id][d^1] = son[k][d];
    son[k][d] = id;
    id = k;
    pushup(son[id][d]);
    pushup(id);
}

void insert(int &id, int x)//插入操作
{
    if(!id) {
        id = New(x);
        return;
    }
    if(x == val[id]) cnt[id]++;
    else {
        int d = x < val[id] ? 0 : 1;
        insert(son[id][d], x);
        if(dat[id] < dat[son[id][d]]) Rotate(id, d^1);
    }
    pushup(id);
}

void Remove(int &id, int x)//删除操作
{
    if(!id) return;
    if(x == val[id]) {
        if(cnt[id] > 1) {
            cnt[id]--;
            pushup(id);
            return;
        }
        if(son[id][0] || son[id][1]) {
            if(!son[id][1] || dat[son[id][0]] > dat[son[id][1]]) {
                Rotate(id, 1);
                Remove(son[id][1], x);
            }
            else Rotate(id, 0), Remove(son[id][0], x);
            pushup(id);
        }
        else id = 0;
        return;
    }
    x < val[id] ? Remove(son[id][0], x) : Remove(son[id][1], x);
    pushup(id);
    return;
}

int query_rank(int id, int x)//查询排名
{
    if(!id) return 0;
    if(x == val[id]) return size[son[id][0]] + 1;
    else if(x < val[id]) return query_rank(son[id][0], x);
    else return size[son[id][0]] + cnt[id] + query_rank(son[id][1], x);
}

int query_val(int id, int rank)//查询排名为rank对应的值
{
    if(!id) return INF;
    if(rank <= size[son[id][0]]) return query_val(son[id][0], rank);
    else if(rank <= size[son[id][0]] + cnt[id]) return val[id];
    else return query_val(son[id][1], rank - size[son[id][0]] - cnt[id]);
}

int query_pre(int x)//查询x的前驱
{
    int id = root;
    int ans;
    while(id) {
        if(val[id] < x) ans = val[id], id = son[id][1];
        else id = son[id][0];
    }
    return ans;
}

int query_next(int x)//查询x的后继
{
    int id = root;
    int ans;
    while(id) {
        if(val[id] > x) ans = val[id], id = son[id][0];
        else id = son[id][1];
    }
    return ans;
}

int main() {
    n = read();
    build();
    for(int i = 1; i <= n; i++) {
        int opt = read(), x = read();
        if(opt == 1) insert(root, x);
        else if(opt == 2) Remove(root, x);
        else if(opt == 3) printf("%d\n", query_rank(root, x) - 1);
        else if(opt == 4) printf("%d\n", query_val(root, x+1));
        else if(opt == 5) printf("%d\n", query_pre(x));
        else if(opt == 6) printf("%d\n", query_next(x));
    }
    return 0;
}