FHQtreap

#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
#include<cstdlib>
using namespace std;
const int N = 100000 + 1100;
const int INF = 0x3f3f3f3f;
int son[N][2],val[N],key[N],size[N],sz;
int root,x,y,z,op;
inline void update(int x){size[x]=size[son[x][1]]+size[son[x][0]]+1;}
inline int New(int V){
    size[++sz]=1;
    val[sz]=V;
    key[sz]=rand();
    son[sz][1]=son[sz][0]=0;
    return sz;
}
inline int merge(int A,int B){
    if(!A||!B)return A^B;
    if(key[A]<key[B]){
        son[A][1]=merge(son[A][1],B);
        update(A);
        return A;
    }
    else{
        son[B][0]=merge(A,son[B][0]);
        update(B);return B;
    }
}
inline void split(int now,int k,int &x,int &y){
    if(!now)x=y=0;
    else{
        if(val[now]<=k)
            x=now,split(son[now][1],k,son[now][1],y);
        else y=now,split(son[now][0],k,x,son[now][0]);
        update(now);
    }
}
inline int Kth(int now,int k){
    if(size[son[now][0]]>=k)return Kth(son[now][0],k);
    if(size[son[now][0]]+1==k)return now;
    return Kth(son[now][1],k-1-size[son[now][0]]);
}
inline void insert(int V){
    split(root,V,x,y);
    root=merge(x,New(V));
    root=merge(root,y);
}
inline void Del(int V){
    split(root,V,x,z);
    split(x,V-1,x,y);
    y=merge(son[y][0],son[y][1]);
    root=merge(x,y);
    root=merge(root,z);
}
inline void Rank(int V){
    split(root,V-1,x,y);
    printf("%d\n",size[x]+1);
    root=merge(x,y);
}
inline void Find(int V){
    printf("%d\n",val[Kth(root,V)]);
}
inline void Pre(int V){
    split(root,V-1,x,y);
    printf("%d\n",val[Kth(x,size[x])]);
    root=merge(x,y);
}
inline void Nxt(int V){
    split(root,V,x,y);
    printf("%d\n",val[Kth(y,1)]);
    root=merge(x,y);
}
int n,a;
int main() {
    srand(20190627);
    scanf("%d",&n);
    while(n--){
        scanf("%d%d",&op,&a);
        switch(op){
            case 1:insert(a);break;
            case 2:Del(a);break;
            case 3:Rank(a);break;
            case 4:Find(a);break;
            case 5:Pre(a);break;
            case 6:Nxt(a);break;
        }    
    }
}