模板_Treap

#include<cstdio>
#include<cstdlib>
#include<iostream>
using namespace std;
struct Node{
Node *ch[2];//左右子树
int r,v,s; //随机优先值，值，节点总数
Node(int v):v(v){ch[0]=ch[1]=NULL;r=rand();s=1;}
bool operator < (const Node &a) const{return r<a.r;}
int comp(int x) const{if(x==v) return -1;return x<v?0:1;}
void maintain(){s=1;if(ch[0]!=NULL) s+=ch[0]->s;if(ch[1]!=NULL) s+=ch[1]->s;}
};
void rotate(Node* &o,int d){//旋转 d=0左旋 d=1右旋
Node* k=o->ch[d^1];o->ch[d^1]=k->ch[d];k->ch[d]=o;
o->maintain();k->maintain();o=k;
}
void insert(Node* &o,int x){//插入x
if(o==NULL) o=new Node(x);
else{
int d=(x<o->v?0:1);
insert(o->ch[d],x);
if(o->ch[d]->r > o->r) rotate(o,d^1);
}
o->maintain();
}
void remove(Node* &o,int x){//删除节点
int d=o->comp(x);
if(d==-1){
Node* u=o;
if(o->ch[0]!=NULL&&o->ch[1]!=NULL){
int d2=(o->ch[0]->r > o->ch[1]->r?1:0);
rotate(o,d2);remove(o->ch[d2],x);
}else{
if(o->ch[0]==NULL) o=o->ch[1];else o=o->ch[0];
delete u;
}
}else remove(o->ch[d],x);
if(o!=NULL) o->maintain();
}
int kth(Node* o,int k){//第k大
if(o==NULL||k<=0||k>o->s) return 0;
int s=(o->ch[1]==NULL?0:o->ch[1]->s);
if(k==s+1) return o->v;
else if(k<=s) return kth(o->ch[1],k);
else return kth(o->ch[0],k-s-1);
}