普通平衡树 Treap
Code:
#include<cstdio> #include<cstdlib> #include<algorithm> using namespace std; struct Node{ Node *ch[2]; int r,v,s,val; int cmp(int x) const{ if(x==v)return -1; return x<v?0:1; } Node(int V){ s=1,val=1;ch[0]=ch[1]=NULL; r=rand();v=V; } void maintain(){ s=val; if(ch[0]!=NULL)s+=ch[0]->s; if(ch[1]!=NULL)s+=ch[1]->s; } }; Node *head; void rotate(Node* &o,int d){ 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){ if(o==NULL)o=new Node(x); else{ int d=o->cmp(x); if(d==-1){ ++(o->val);++(o->s);return; } insert(o->ch[d],x); o->maintain(); if((o->ch[d]->r)>o->r)rotate(o,d^1); } } void erase(Node* &o,int x){ int d=o->cmp(x); if(d==-1){ if(o->ch[0]==NULL){ (o->val)--;(o->s)--; if(o->val==0)o=o->ch[1]; } else if(o->ch[1]==NULL){ (o->val)--;(o->s)--; if(o->val==0)o=o->ch[0]; } else{ int d2=(o->ch[0]->r)>(o->ch[1]->r)?1:0; rotate(o,d2); erase(o->ch[d2],x); o->maintain(); } }else { erase(o->ch[d],x); o->maintain(); } } int rank1(Node *o,int x){ //x的排名 int d=o->cmp(x); int lsize=(o->ch[0]==NULL)?0:o->ch[0]->s; if(d==0)return rank1(o->ch[0],x); if(d==1)return lsize+o->val+rank1(o->ch[1],x); return lsize+1; } int kth(Node *o,int R){ //第k大 int lsize=(o->ch[0]==NULL)?0:o->ch[0]->s; if(R<=lsize)return kth(o->ch[0],R); if(lsize+o->val>=R)return o->v; return kth(o->ch[1],R-lsize-o->val); } int ans; void find1(Node *o,int x){ //前驱 if(o->v<x){ans=max(ans,o->v);if(o->ch[1]!=NULL)find1(o->ch[1],x);} else if(o->ch[0]!=NULL)find1(o->ch[0],x); } void find2(Node *o,int x){ //后继 if(o->v>x){ans=min(ans,o->v);if(o->ch[0]!=NULL)find2(o->ch[0],x);} else if(o->ch[1]!=NULL)find2(o->ch[1],x); } int main() { int n; scanf("%d",&n); for(int i=1;i<=n;++i) { int opt,x; scanf("%d%d",&opt,&x); if(opt==1)insert(head,x); if(opt==2)erase(head,x); if(opt==3)printf("%d\n",rank1(head,x)); if(opt==4)printf("%d\n",kth(head,x)); if(opt==5){ans=-10000000;find1(head,x);printf("%d\n",ans);} if(opt==6){ans=10000000;find2(head,x);printf("%d\n",ans);} } return 0; }