Root of AVL Tree

04-树5 Root of AVL Tree（25 分）

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 the 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 

 

 #include<iostream>
 using namespace std;
 struct treenode{
        int data,h;
        treenode* left=NULL;
        treenode* right=NULL;
 };
 using tree=treenode*;
 int height(tree t){
     //cout<<"height(tree t)"<<endl;
     if(!t) return ;
     return max(height(t->left),height(t->right))+;
 }
 tree RotateLL(tree t){
     //cout<<" RotateLL(tree t)"<<endl;
     tree a=t->left;
     t->left=a->right;
     a->right=t;
     a->h=max(height(a->left),height(a->right))+;
     t->h=max(height(t->left),height(t->right))+;
     return a;
 }
 tree RotateRR(tree t){
    //cout<<"RotateRR(tree t)"<<endl;
     tree a=t->right;
     t->right=a->left;
     a->left=t;
     a->h=max(height(a->left),height(a->right))+;
     t->h=max(height(t->left),height(t->right))+;
     return a;
 }
 tree RotateLR(tree t){
 //cout<<"RotateLR(tree t)"<<endl;
     t->left=RotateRR(t->left);
     return RotateLL(t);
 }
 tree RotateRL(tree t){
    //cout<<"RotateRL(tree t)"<<endl;
     t->right=RotateLL(t->right);
     return RotateRR(t);
 }
 tree insert(tree t,int v){
 //cout<<" insert(tree t,int v)"<<endl;
     if(t==NULL){
        t=new treenode();
        t->data=v; t->h=;
        return t;
     }else if(v<t->data){
        t->left=insert(t->left,v);
        if(height(t->left)-height(t->right)==)
        if(v<t->left->data)
        t=RotateLL(t);
        else t=RotateLR(t);
     }else{
        t->right=insert(t->right,v);
        if(height(t->left)-height(t->right)==-)
        if(v>t->right->data)
        t=RotateRR(t);
        else t=RotateRL(t);
 }
     t->h=height(t);
     return t;
 }
 int main(){
     int n;
     cin>>n;
     tree t=NULL;
     for(int i=;i<n;i++){
         int v; cin>>v;
         t=insert(t,v);
     }
     cout<<t->data<<endl;
     return ;
 }