hdu 4006 The kth great number

        动态询问一些数中第k大的数（没有删除操作）。为了学习AVL树，用AVL码的，居然1A了，但是效率并不比普通二叉树有所提高。做法是在AVL树的基础上，维护每个节点的大小，根据大小信息查找第k大。

#include <iostream>    #include <stdio.h>    #include <string>    #include <map>    #include <vector>    #include <stack>    #include <queue>    #include <string.h>    #include <algorithm>    #include <math.h>        using namespace std;    struct avl{int data;int height;avl* pleft;avl* pright;int size;};int Height(avl* pNode){if(NULL==pNode)return -1;return pNode->height;}int Size(avl* pNode){if(NULL==pNode)return 0;return pNode->size;}avl* LLRotate(avl* pNode){avl* l=pNode->pleft;pNode->pleft=l->pright;l->pright=pNode;pNode->size=Size(pNode->pleft)+Size(pNode->pright)+1;l->size=Size(l->pleft)+Size(l->pright)+1;pNode->height=max(Height(pNode->pleft),Height(pNode->pright))+1;l->height=max(Height(l->pleft),Height(l->pright))+1;return l;}avl* RRRotate(avl* pNode){avl* r=pNode->pright;pNode->pright=r->pleft;r->pleft=pNode;pNode->size=Size(pNode->pleft)+Size(pNode->pright)+1;r->size=Size(r->pleft)+Size(r->pright)+1;pNode->height=max(Height(pNode->pleft),Height(pNode->pright))+1;r->height=max(Height(r->pleft),Height(r->pright))+1;return r;}avl* LRRotate(avl* pNode){pNode->pleft=RRRotate(pNode->pleft);return LLRotate(pNode);}avl* RLRotate(avl* pNode){pNode->pright=LLRotate(pNode->pright);return RRRotate(pNode);}avl* insert(avl* pNode,int data){if(pNode==NULL){pNode=new avl();pNode->data=data;pNode->height=0;pNode->size=1;}else if(data>pNode->data){pNode->pleft=insert(pNode->pleft,data);pNode->size++;if(Height(pNode->pleft)-Height(pNode->pright)==2){//不平衡 if(data>pNode->pleft->data){pNode=LLRotate(pNode);}else{pNode=LRRotate(pNode);}}}else{pNode->pright=insert(pNode->pright,data);pNode->size++;if(Height(pNode->pright)-Height(pNode->pleft)==2){//不平衡 if(data<pNode->pright->data){pNode=RRRotate(pNode);}else{pNode=RLRotate(pNode);}}}pNode->height=max(Height(pNode->pleft),Height(pNode->pright));return pNode;}int query(avl* pNode,int q){int lsiz=0;if(pNode->pleft)lsiz=pNode->pleft->size;int rsiz=0;if(pNode->pright)rsiz=pNode->pright->size;if(lsiz+1==q) return pNode->data;else if(lsiz>=q) return query(pNode->pleft,q);else return query(pNode->pright,q-1-lsiz);}int main(){int n,k;while(cin>>n>>k){avl* root=NULL;for(int i=1;i<=n;i++){char op[2];scanf("%s",op);if(op[0]=='I'){int num;scanf("%d",&num);root=insert(root,num);}else{int ans=query(root,k);printf("%d\n",ans);}}}return 0;}