poj 1442 名次树

这回要求的是第k小的元素，

参考了ljl大神的模板，orz

 //insert 插入
 //remove 删除
 //_find 查找
 //kth 返回root为根的树中第k小的元素
 //treap插入、删除、查询时间复杂度均为O(logn)
 #include <iostream>
 #include <cstring>
 #include <cstdlib>
 #include <ctime>
 #include <cstdio>
 using namespace std;
 int a[],n,m;
 struct Node
     {
         Node *ch[];
         int r,v,s;
         Node(int v):v(v)
             {s=;ch[]=ch[]=NULL;r=rand();}
         int cmp(int x) const{
             if(x==v)return(-);
             return (x<v)?():();
         }
         void maintain(){
             s=;
             if(ch[]!=NULL)s+=ch[]->s;
             if(ch[]!=NULL)s+=ch[]->s;
         }
     };
 void rotate(Node* &o,int d)
     {
         Node* k=o->ch[d^];
         o->ch[d^]=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=(x<o->v)?:;
             insert(o->ch[d],x);
             if((o->r)<(o->ch[d]->r))
                 rotate(o,d^);
         }
         o->maintain();
     }
 void remove(Node* &o,int x)
     {
         int d=o->cmp(x);
         if(d==-){
             Node* u=o;
             if(o->ch[]==NULL){o=o->ch[];delete u;}else
             if(o->ch[]==NULL){o=o->ch[];delete u;}else {
                 int c=(o->ch[])>(o->ch[])?():();
                 rotate(o,c);
                 remove(o->ch[c],x);
             }
         }
         else remove(o->ch[d],x);
         if(o!=NULL) o->maintain();
     }
 int find(Node* &o,int x)
     {
         while(o!=NULL){
             int d=o->cmp(x);
             if(d==-)
                 return ;
             else
                 o=o->ch[d];
         }
         return ;
     }
 int kth(Node* o,int k)
     {
         while(o!=NULL){
             int lchsize=(o->ch[]!=NULL)?
                         (o->ch[]->s):;
             if(lchsize+==k)
                 return o->v;
             else {
                 int d=(lchsize<k);
                 o=o->ch[d];
                 k-=d*(lchsize+);
             }
         }
         return ;
     }

 int main()
 {
     Node* root=NULL;
     int u,ans,p=;
     srand(time());

     cin>>m>>n;
     for(int i=;i<m;i++)
         cin>>a[i];
     for(int i=;i<=n;i++)
     {
         cin>>u;
         while(p<u)
             insert(root,a[p++]);
         ans=kth(root,i);
         cout<<ans<<endl;
     }
     return ;
 }