模板—treap

 #include<iostream>
 #include<cstdio>
 #include<cstdlib>
 #define INF 0x7fffffff
 using namespace std ;
 struct treap
 {
     int l,r,val,dat,cnt,size;
     #define l(x) tr[x].l
     #define r(x) tr[x].r
     #define val(x) tr[x].val
     #define dat(x) tr[x].dat
     #define cnt(x) tr[x].cnt
     #define size(x) tr[x].size
 }tr[];
 int tot,root,n;

 int New(int val)
 {
     ++tot;
     val(tot)=val;
     dat(tot)=rand();
     size(tot)=cnt(tot)=;
     return tot;
 }
 void updata(int x)
 {
     size(x)=cnt(x)+size(l(x))+size(r(x));
 }
 void build()
 {
     New(-INF),New(INF);
     root=;
     r()=;
     updata(root);
 }
 void zig(int &p)//you
 {
     int q=l(p);
     l(p)=r(q);
     r(q)=p;
     updata(p),updata(q);
     p=q;
 }
 void zag(int &p)//zuo
 {
     int q=r(p);
     r(p)=l(q);
     l(q)=p;
     updata(p),updata(q);
     p=q;
 }
 int grbv(int p,int val)
 {
     if(!p)return ;
     if(val==val(p))return size(l(p))+;
     if(val(p)>val) return grbv(l(p),val);
     return grbv(r(p),val)+size(l(p))+cnt(p);
 }
 int gvbr(int p,int rank)
 {
     if(!p)return INF;
     if(size(l(p))>=rank)return gvbr(l(p),rank);
     if(size(l(p))+cnt(p)>=rank)return val(p);
     return gvbr(r(p),rank-size(l(p))-cnt(p));
 }
 void insert(int &p,int val)
 {
     if(!p){p=New(val);return;}
     if(val(p)==val){cnt(p)++;updata(p);return;}
     if(val(p)>val)
     {
         insert(l(p),val);
         if(dat(l(p))>dat(p))zig(p);
     }
     else
     {
         insert(r(p),val);
         if(dat(r(p))>dat(p))zag(p);
     }
     updata(p);
 }
 void remove(int &p,int val)
 {
     if(!p)return;
     if(val(p)==val)
     {
         if(cnt(p)>){cnt(p)--;updata(p);return;}
         if(l(p) || r(p))
         {
             if(r(p)== || dat(l(p))>dat(r(p)))
                 zig(p),remove(r(p),val);
             else
                 zag(p),remove(l(p),val);
             updata(p);
         }
         else p=;
         return;
     }
     val<val(p)?remove(l(p),val):remove(r(p),val);
     updata(p);
 }
 int getpre(int val)
 {
     int ans=,p=root;
     while(p)
     {
         if(val(p)==val)
         {
             if(l(p)>)
             {
                 p=l(p);
                 while(r(p)>)p=r(p);
                 ans=p;
             }
             break;
         }
         if(val(p)<val && val(p)>val(ans))ans=p;
         p=val<val(p)?l(p):r(p);
     }
     return val(ans);
 }
 int getnext(int val)
 {
     int ans=,p=root;
     while(p)
     {
         if(val(p)==val)
         {
             if(r(p)>)
             {
                 p=r(p);
                 while(l(p)>)p=l(p);
                 ans=p;
             }
             break;
         }
         if(val(p)>val && val(p)<val(ans))ans=p;
         p=val<val(p)?l(p):r(p);
     }
     return val(ans);
 }
 signed main()
 {
 //    freopen("input2.in","r",stdin);

     build();
     cin>>n;
     int  opt,x;
     for(int i=;i<=n;i++)
     {
         cin>>opt>>x;
         if(opt==)insert(root,x);
         if(opt==)remove(root,x);
         if(opt==)cout<<grbv(root,x)-<<endl;
         if(opt==)cout<<gvbr(root,x+)<<endl;
         if(opt==)cout<<getpre(x)<<endl;
         if(opt==)cout<<getnext(x)<<endl;
     }
 }