POJ1442-查询第K大-Treap模板题

模板题，以后要学splay，大概看一下treap就好了。

 #include <cstdio>
 #include <algorithm>
 #include <cstring>

 using namespace std;

 const int maxn = 3e5+;
 int num[maxn],st[maxn];

 struct Treap{
     int size;
     int key,fix;
     Treap *ch[];

     Treap(int key)
     {
         size = ;
         fix = rand();
         this->key = key;
         ch[] = ch[] = NULL;
     }
     int compare(int x) const
     {
         if(x == key) return -;
         return x < key ?  : ;
     }
     void Maintain()
     {
         size = ;
         if(ch[] != NULL) size += ch[]->size;
         if(ch[] != NULL) size += ch[]->size;
     }
 };

 void Rotate(Treap* &t ,int d)
 {
     Treap *k = t->ch[d^];
     t->ch[d^] = k->ch[d];
     k->ch[d] = t;
     t->Maintain();
     k->Maintain();
     t = k;
 }

 void Insert(Treap* &t,int x)
 {
     if(t == NULL) t = new Treap(x);
     else
     {
         int d = x < t->key ?  : ;
         Insert(t->ch[d],x);
         if(t->ch[d]->fix > t->fix)
             Rotate(t,d^);
     }
     t->Maintain();
 }

 void Delete(Treap* &t,int x)
 {
     int d = t->compare(x);
     if(d == -)
     {
         Treap *tmp = t;
         if(t->ch[] == NULL)
         {
             t = t->ch[];
             delete tmp;
             tmp = NULL;
         }
         else if(t->ch[] == NULL)
         {
             t = t->ch[];
             delete tmp;
             tmp = NULL;
         }
         else
         {
             int k = t->ch[]->fix > t->ch[]->fix ?  : ;
             Rotate(t,k);
             Delete(t->ch[k],x);
         }
     }
     else Delete(t->ch[d],x);
     if(t!=NULL) t->Maintain();
 }

 bool Find(Treap *t,int x)
 {
     while(t != NULL)
     {
         int d = t->compare(x);
         if(d == -) return true;
         t = t->ch[d];
     }
     return false;
 }

 int Kth(Treap *t,int k)
 {
     if(t == NULL || k <=  || k > t->size)
         return -;
     if(t->ch[] == NULL && k == )
         return t->key;
     if(t->ch[] == NULL)
         return Kth(t->ch[],k-);
     if(t->ch[]->size >= k)
         return Kth(t->ch[],k);
     if(t->ch[]->size +  == k)
         return t->key;
     return Kth(t->ch[],k--t->ch[]->size);
 }

 int Rank(Treap *t,int x)
 {
     int r;
     if(t->ch[] == NULL) r = ;
     else r = t->ch[]->size;
     if(x == t->key) return r+;
     if(x < t->key)
         return Rank(t->ch[],x);
     return r++Rank(t->ch[],x);
 }

 void DeleteTreap(Treap* &t)
 {
     if(t == NULL) return;
     if(t->ch[] != NULL) DeleteTreap(t->ch[]);
     if(t->ch[] != NULL) DeleteTreap(t->ch[]);
     delete t;
     t = NULL;
 }

 int save[maxn];
 int M,N;

 int main()
 {
     while(~scanf("%d%d",&M,&N))
     {
         for(int i=;i<=M;i++)
             scanf("%d",&save[i]);
         Treap *root = NULL;
         int cnt = ;
         for(int i=,x;i<=N;i++)
         {
             scanf("%d",&x);
             for(int j = cnt;j <= x;j++)
                 Insert(root,save[j]);
             cnt = x+;
             printf("%d\n",Kth(root,i));
         }
         DeleteTreap(root);
     }
 }