模板——无旋Treap

 #include "bits/stdc++.h"

 using namespace std;

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

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

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

 struct Treap{
     Treap *son[];
     int fix,val,size;
     Treap (int v){
         size=,val=v,fix=rand();
         son[]=son[]=NULL;
     }
     inline void update(){
         size=+size(son[])+size(son[]);
     }
 }*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[]=merge(a->son[],b);a->update();return a;
     }else   {
         b->son[]=merge(a,b->son[]);b->update();return b;
     }
 }

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

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

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

 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,);
     root=merge(x.first,y.second);
 }

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