平衡二叉树——A1066.Root of AVL Tree（25） 注意求平衡因子的函数，更新树高的函数，左旋和右旋的对称性：互换rchild与lchild即可，注意哪些函数需要用引用，哪些不需要

#include <bits/stdc++.h>
#include <stdio.h>
#include <stdlib.h>
#include <queue>
using namespace std;
const int maxn = 110;
struct node{
    int v,height;
    node *lchild,*rchild;
}*root;
//生成新节点,v为节点权值
node *newNode(int v){
    node* Node = new node;
    Node->v = v;
    Node->height = 1;
    Node->lchild = NULL;
    Node->rchild = NULL;
    return Node;
}
//获取以root为根节点的子树的当前height
int getHeight(node *root){
    if(root == NULL){
        return 0;
    }else{
        return root->height;
    }
}
//更新节点root的height
void updateHeight(node* root){
    root->height = max(getHeight(root->lchild),getHeight(root->rchild)) + 1;
}
//计算节点的平衡因子
int getBalanceFactor(node* root){
    return getHeight(root->lchild) - getHeight(root->rchild);
}
//左旋
void L(node* &root){
    node *temp = root->rchild;
    root->rchild = temp->lchild;
    temp->lchild = root;
    updateHeight(root);
    updateHeight(temp);
    root = temp;
}
//右旋
void R(node* &root){
    node *temp = root->lchild;
    root->lchild = temp->rchild;
    temp->rchild = root;
    updateHeight(root);
    updateHeight(temp);
    root = temp;
}
//插入权值为v的节点
void insert(node* &root,int v){
    if(root == NULL){
        root = newNode(v);
        return;
    }
    if(v < root->v){
        insert(root->lchild,v);
        updateHeight(root);
        if(getBalanceFactor(root) == 2){
            if(getBalanceFactor(root->lchild) == 1){//LL型
                R(root);
            }else if(getBalanceFactor(root->lchild) == -1){
                L(root->lchild);
                R(root);
            }
        }
    }
    else{
        insert(root->rchild,v);
        updateHeight(root);
        if(getBalanceFactor(root) == -2){
            if(getBalanceFactor(root->rchild) == -1){
                L(root);
            }else if(getBalanceFactor(root->rchild) == 1){
                R(root->rchild);
                L(root);
            }
        }
    }
}
//AVL树的建立
node *Create(int data[],int n){
    node* root = NULL;
    for(int i = 0;i<n;++i){
        insert(root,data[i]);
    }
    return root;
}
int main(){
    int n,v;
    scanf("%d",&n);
    for(int i=0;i<n;++i){
        scanf("%d",&v);
        insert(root,v);
    }
    printf("%d\n",root->v);
    system("pause");
    return 0;
}