模板——无旋Treap

#include "bits/stdc++.h"

using namespace std;

inline int read(){
    int s=0,k=1;char ch=getchar();
    while(ch<'0'|ch>'9') ch=='-'?k=-1:0,ch=getchar();
    while(ch>47&ch<='9') s=s*10+(ch^48),ch=getchar();
    return s*k;
}

const int N=1e5+5,inf=0x7fffffff;

#define size(t) (t?t->size:0)

struct Treap{
    Treap *son[2];
    int fix,val,size;
    Treap (int v){
        size=1,val=v,fix=rand();
        son[0]=son[1]=NULL;
    }
    inline void update(){
        size=1+size(son[0])+size(son[1]);
    }
}*root;

typedef pair<Treap*,Treap*> D;

inline Treap *merge(Treap *a,Treap *b){
    if(!a||!b) return a?a:b;
    if(a->fix<b->fix){
        a->son[1]=merge(a->son[1],b);a->update();return a;
    }else   {
        b->son[0]=merge(a,b->son[0]);b->update();return b;
    }
}

inline D split(Treap *p,int k){
    if(!p)  return D(NULL,NULL);
    D y;
    if(size(p->son[0])>=k) 
        y=split(p->son[0],k),p->son[0]=y.second,p->update(),y.second=p;
    else
        y=split(p->son[1],k-1-size(p->son[0])),p->son[1]=y.first,p->update(),y.first=p;
    return y;
}

inline int get_rnk(int val){
    int ret=0;
    for(Treap *t=root;t;t=t->son[val>t->val])
        if(t->val<val)  ret+=1+size(t->son[0]);
    return ret;
}

inline int findkth(int k){
    D x=split(root,k-1);
    D y=split(x.second,1);
    Treap *ans=y.first;
    root=merge(merge(x.first,ans),y.second);
    return ans?ans->val:0;
}

inline void insert(int val){
    int k=get_rnk(val);
    D x=split(root,k);
    Treap *p=new Treap(val);
    root=merge(merge(x.first,p),x.second);
}

inline void erase(int val){
    int k=get_rnk(val);
    D x=split(root,k);
    D y=split(x.second,1);
    root=merge(x.first,y.second);
}

int main(){    
    freopen("phs.in","r",stdin);
    freopen("phs.out","w",stdout);
    srand(1228);
    int m,opt,x;m=read();
    while(m--){
        opt=read(),x=read();
        switch(opt)
        {
            case 1:insert(x);break;
            case 2:erase(x);break;
            case 3:printf("%d
",get_rnk(x)+1);break;
            case 4:printf("%d
",findkth(x));break;
            case 5:printf("%d
",findkth(get_rnk(x)));break;
            case 6:printf("%d
",findkth(get_rnk(x+1)+1));break;
        }
    }
}