【题解】 bzoj1503: [NOI2004]郁闷的出纳员 （Splay）

int rk(int x){
  int now=root;del(low);

int rk(int x){
  del(low);int now=root;
  if(x>node[now].siz)return -1;
  while(1){
    pushdown(now);
    if(!now)return -1;
    if(node[rs(now)].siz>=x){now=node[now].ch[1];}
    else if(node[rs(now)].siz+node[now].cnt>=x){Splay(now,root);return node[now].val;}
    else {x-=(node[rs(now)].siz+node[now].cnt);now=node[now].ch[0];}
  }
}

//It is coded by Ning_Mew on 5.8
#include<bits/stdc++.h>
#define rs(x) node[x].ch[1]
#define ls(x) node[x].ch[0]
#define fa(x) node[x].fa
#define root node[0].ch[1]
using namespace std;

const int maxn=1e5+10007;

int n,low,tot=0,ans=0;
struct Node{
  int fa,ch[2],val,cnt,siz,lazy;
}node[maxn];

void update(int x){node[x].siz=node[ls(x)].siz+node[rs(x)].siz+node[x].cnt;}
void connect(int x,int fa,int how){node[x].fa=fa;node[fa].ch[how]=x;}
int ident(int x){return x==node[fa(x)].ch[0]?0:1;}
void pushdown(int x){
  if(node[x].lazy){ 
    int lz=node[x].lazy;node[x].lazy=0;
    if(ls(x))node[ls(x)].val+=lz,node[ls(x)].lazy+=lz;
    if(rs(x))node[rs(x)].val+=lz,node[rs(x)].lazy+=lz;return;
  }
}
void rorate(int x){
  int Y=fa(x),R=fa(Y);int Yson=ident(x),Rson=ident(Y);
  pushdown(Y);pushdown(x);
  connect(node[x].ch[Yson^1],Y,Yson);
  connect(Y,x,Yson^1);
  connect(x,R,Rson);
  update(Y);update(x);
}
void Splay(int x,int goal){
  goal=fa(goal);
  while(fa(x)!=goal){
    if(fa(fa(x))==goal)rorate(x);
    else if(ident(x)==ident(fa(x)))rorate(fa(x)),rorate(x);
    else rorate(x),rorate(x);
  }return;
}
int newnode(int x,int fa){node[++tot].val=x;node[tot].siz=node[tot].cnt=1;node[tot].fa=fa;return tot;}
void ins(int x){
  int now=root;
  if(!now){newnode(x,0);root=tot;return;}
  while(now){
    node[now].siz++;pushdown(now);
    if(node[now].val==x){node[now].cnt++;Splay(now,root);/*root=now;*/return;}
    int nxt=x<node[now].val?0:1;
    if(!node[now].ch[nxt]){int pl=newnode(x,now);node[now].ch[nxt]=pl;Splay(pl,root);/*root=pl;*/return;}
    now=node[now].ch[nxt];
  }
}
void pr(int now){
  if(!now)return;
  cout<<"pr:"<<now<<‘ ‘<<node[now].siz<<‘ ‘<<node[now].val<<‘ ‘<<node[ls(now)].val<<‘ ‘<<node[rs(now)].val<<‘ ‘<<node[now].cnt<<endl;
  pr(ls(now));pr(rs(now));//update(now);
}
void del(int x){
  ins(x);
  int now=root;
  if(ls(now))ans+=node[ls(now)].siz;
  if(node[now].cnt==1){
    connect(rs(now),0,1);update(root);
  }
  else {node[now].cnt--;node[now].ch[0]=0;node[ls(now)].fa=0;update(now);}
  return;
}
int rk(int x){
  del(low);int now=root;
  if(x>node[now].siz)return -1;
  while(1){
    pushdown(now);
    if(!now)return -1;
    if(node[rs(now)].siz>=x){now=node[now].ch[1];}
    else if(node[rs(now)].siz+node[now].cnt>=x){Splay(now,root);return node[now].val;}
    else {x-=(node[rs(now)].siz+node[now].cnt);now=node[now].ch[0];}
  }
}
int main(){
  scanf("%d%d",&n,&low);
  int x;char ch;
  for(int i=1;i<=n;i++){
    cin>>ch;scanf("%d",&x);
    if(ch==‘I‘){if(x<low)continue;ins(x);}
    if(ch==‘A‘){node[root].val+=x;node[root].lazy+=x;}
    if(ch==‘S‘){node[root].val-=x;node[root].lazy-=x;del(low);}
    if(ch==‘F‘){printf("%d\n",rk(x));}
  }
  printf("%d\n",ans);
  return 0;
}