学步园

题目：http://www.lydsy.com/JudgeOnline/problem.php?id=1503

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

using namespace std;

struct Node
{
    int val,size,cnt,lazy;
    Node *pre,*ch[2];
    Node()
    {
        size = lazy = cnt = 0;
    }
};

Node *null,*root,*newNode,*last;

void Init()      //新增的newNode为root的父亲节点
{
    null = new(Node);
    root = null;
    newNode = new(Node);
    newNode->ch[0] = root;
    newNode->ch[1] = null;
    root->pre = newNode;
}

void Update(Node* &t)
{
    t->size = t->cnt + t->ch[0]->size + t->ch[1]->size;
    t->ch[0]->pre = t->ch[1]->pre = t;
}

int F(Node *t)    // 判断当前点的是左孩子还是右孩子
{
    return t->pre->ch[1] == t;
}

void Rotate(Node* t,int c)
{
    Node *k = t->ch[c];
    k->pre = t->pre;
    t->pre->ch[F(t)] = k;
    t->ch[c] = k->ch[!c];
    k->ch[!c] = t;
    Update(t);
    Update(k);
}

void Splay(Node* last,Node* newNode)
{
    Node *tmp = last;
    while(tmp->pre != newNode)
    {
        if(tmp->pre->pre == newNode)
            Rotate(tmp->pre,F(tmp));
        else if(F(tmp->pre) == F(tmp))
        {
            Rotate(tmp->pre->pre,F(tmp->pre));
            Rotate(tmp->pre,F(tmp));
        }
        else
        {
            Rotate(tmp->pre,F(tmp));
            Rotate(tmp->pre,F(tmp));
        }
    }
    root = newNode->ch[0];
}

void PushDown(Node* &t)
{
    t->ch[0]->val += t->lazy;
    t->ch[0]->lazy += t->lazy;
    t->ch[1]->val += t->lazy;
    t->ch[1]->lazy += t->lazy;
    t->lazy = 0;
}

void Insert(Node* &t,int x)
{
    if(t == null)
    {
        t=new(Node);
        t->val = x;
        t->ch[0] = t->ch[1] = null;
        t->size = t->cnt = 1;
        last = t;
        return;
    }
    PushDown(t);
    if(t->val == x) t->cnt++;
    if(t->val > x)  Insert(t->ch[0],x);
    if(t->val < x)  Insert(t->ch[1],x);
    Update(t);
}

Node *Find(Node *t,int x)  //查找后继，包括等于自己
{
    if(t == null) return null;
    PushDown(t);
    if(t->val == x) return t;
    if(t->val < x)  return Find(t->ch[1],x);
    if(t->val > x)
    {
        Node *tmp = Find(t->ch[0],x);
        if(tmp != null) return tmp;
        else return t;
    }
}

int Query(Node *t,int k)    //询问第K大
{
    if(t == null) return -1;
    PushDown(t);
    if(t->ch[1]->size >= k) return Query(t->ch[1],k);
    if(t->ch[1]->size + t->cnt >= k) return t->val;
    return Query(t->ch[0],k - t->ch[1]->size - t->cnt);
}

void Work()
{
    int n,limit;
    scanf("%d%d%*c",&n,&limit);
    int x,ans = 0;
    while(n--)
    {
        char c;
        scanf("%c %d%*c",&c,&x);
        if(c == 'I'&&x < limit) continue;
        if(c == 'I')
        {
            Insert(newNode->ch[0],x);
            Update(newNode);
            Splay(last,newNode);
        }
        else if(c == 'A')
        {
            root->val += x;
            root->lazy += x;
        }
        else if(c == 'S')
        {
            last = null;
            last = Find(root,limit + x);
            if(last == null)
            {
                ans += root->size;
                root = null;
                newNode->ch[0] = root;
                Update(newNode);
            }
            else
            {
                Splay(last,newNode);
                ans += root->ch[0]->size;
                root->ch[0] = null;
                root->val -= x;
                root->lazy -= x;
                Update(root);
            }
        }
        else if(c == 'F')
            printf("%d\n",Query(root,x));
    }
    printf("%d\n",ans);
}

int main()
{
    Init();
    Work();
    return 0;
}