pat1066. Root of AVL Tree (25)

1066. Root of AVL Tree (25)

时间限制

100 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CHEN, Yue

An AVL tree is a self-balancing binary search tree. In an AVL tree, the heights of the two child subtrees of any node differ by at most one; if at any time they differ by more than one, rebalancing is done to restore this property. Figures 1-4 illustrate the rotation rules.

    

    

Now given a sequence of insertions, you are supposed to tell the root of the resulting AVL tree.

Input Specification:

Each input file contains one test case. For each case, the first line contains a positive integer N (<=20) which is the total number of keys to be inserted. Then N distinct integer keys are given in the next line. All the numbers in a line are separated by a space.

Output Specification:

For each test case, print ythe root of the resulting AVL tree in one line.

Sample Input 1:

5
88 70 61 96 120

Sample Output 1:

70

Sample Input 2:

7
88 70 61 96 120 90 65

Sample Output 2:

88

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提交代码

 #include<cstdio>
 #include<cstring>
 #include<iostream>
 #include<stack>
 #include<set>
 #include<map>
 #include<queue>
 #include<algorithm>
 using namespace std;
 struct AVLtreenode{
     int h,v;
     AVLtreenode *l,*r;
 };
 #define max(a,b) (a>b?a:b)
 int GetHeight(AVLtreenode *root){
     if(!root){
         return ;
     }
     return root->h;
 }
 AVLtreenode* AVLRightRotation(AVLtreenode* root){
     AVLtreenode* temp=root->r;
     root->r=temp->l;
     temp->l=root;
     root->h=max(GetHeight(root->l),GetHeight(root->r))+;
     temp->h=max(GetHeight(temp->r),GetHeight(root))+;
     return temp;
 }
 AVLtreenode* AVLLeftRotation(AVLtreenode* root){
     AVLtreenode* temp=root->l;
     root->l=temp->r;
     temp->r=root;
     root->h=max(GetHeight(root->l),GetHeight(root->r))+;
     temp->h=max(GetHeight(temp->l),GetHeight(root))+;
     return temp;
 }
 AVLtreenode* AVLRightLeftRotation(AVLtreenode* root){
     root->r=AVLLeftRotation(root->r);
     root=AVLRightRotation(root);
     return root;
 }
 AVLtreenode* AVLLeftRightRotation(AVLtreenode* root){
     root->l=AVLRightRotation(root->l);
     root=AVLLeftRotation(root);
     return root;
 }
 AVLtreenode* AVLInsert(int num,AVLtreenode *root){
     if(!root){

         //cout<<1<<endl;

         root=new AVLtreenode();
         root->h=;
         root->l=root->r=NULL;
         root->v=num;
         return root;
     }
     //cout<<2<<endl;
     if(root->v>num){//插入左子树
         root->l=AVLInsert(num,root->l);
         if(GetHeight(root->l)-GetHeight(root->r)==){//需要左旋
             if(root->l->v>num){//单左旋
                 root=AVLLeftRotation(root);
             }
             else{//左右旋
                 root=AVLLeftRightRotation(root);
             }
         }
     }
     else{
         root->r=AVLInsert(num,root->r);
         if(GetHeight(root->r)-GetHeight(root->l)==){//
             if(root->r->v<num){//
                 root=AVLRightRotation(root);
             }
             else{//
                 root=AVLRightLeftRotation(root);
             }
         }
     }
     root->h=max(GetHeight(root->l),GetHeight(root->r))+;
     return root;
 }
 int main(){
     //freopen("D:\\INPUT.txt","r",stdin);
     int n;
     scanf("%d",&n);
     int i,num;
     AVLtreenode *root=NULL;
     for(i=;i<n;i++){
         scanf("%d",&num);

         //cout<<"i: "<<i<<endl;

         root=AVLInsert(num,root);
     }
     cout<<root->v<<endl;
     return ;
 }