PAT A1066 Root of AVL Tree (25分)

題目鏈接：https://pintia.cn/problem-sets/994805342720868352/problems/994805404939173888

題目描述
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.

輸入
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.C

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

樣例輸入
5
88 70 61 96 120

樣例輸出
70

代碼

#include<cstdio>
#include<algorithm>
using namespace std;

typedef struct node;
typedef node * tree;
struct node {
    int v;
    int heigh;
    tree L,R;
};

int getheigh(tree root){
    if(root==NULL) return 0;
    return root->heigh;
}

void updataheigh(tree root){
    root->heigh=max(getheigh(root->L),getheigh(root->R))+1;
}

int getBalance(tree root){
    return getheigh(root->L)-getheigh(root->R);
}

void L(tree &root){
    tree temp;
    temp=root->R;
    root->R=temp->L;
    temp->L=root;
    updataheigh(root);
    updataheigh(temp);
    root=temp;
}

void R(tree &root){
    tree temp;
    temp=root->L;
    root->L=temp->R;
    temp->R=root;
    updataheigh(root);
    updataheigh(temp);
    root=temp;
}

void insertt(tree &root,int v){
    if(root==NULL){
        root=new node;
        root->v=v;
        root->heigh=1;
        root->L=root->R=NULL;
        return;
    }
    if(v<root->v){
        insertt(root->L,v);
        updataheigh(root);
        if(getBalance(root)==2){
            if(getBalance(root->L)==1){
                R(root);
            }
            else if(getBalance(root->L)==-1){
                L(root->L);
                R(root);
            }
        }
    }
    else{
        insertt(root->R,v);
        updataheigh(root);
        if(getBalance(root)==-2){
            if(getBalance(root->R)==-1){
                L(root);
            }
            else if(getBalance(root->R)==1){
                R(root->R);
                L(root);
            }
        }
    }

}

int main(){
    int n;
    scanf("%d",&n);
    int x;
    tree root;
    root=NULL;
    for(int i=0;i<n;i++){
        scanf("%d",&x);
        insertt(root,x);
    }
    printf("%d\n",root->v);
    return 0;
}