A1066 Root of AVL Tree [avl 插入/模板题]

#include<iostream>
#include<vector>
#include<queue>
#include<stack>
#include<string>
#include<math.h>
#include<algorithm>
using namespace std;
const int maxn = 1001;
struct node
{
	int v, height;
	node* left, * right;
}*root;

node* newnode(int v)
{
	node* Node = new node;
	Node->v = v;
	Node->height = 1;
	Node->left = Node->right = NULL;
	return Node;
}

int getheight(node* root)
{
	if (root == NULL) return 0;
	return root->height;
}

void updataheight(node* root)
{
	root->height = max(getheight(root->left), getheight(root->right)) + 1;
}

int getbalancefactor(node* root)
{
	return getheight(root->left) - getheight(root->right);
}

void l(node* &root)
{
	node* temp = root->right;
	root->right = temp->left;
	temp->left = root;
	updataheight(root);
	updataheight(temp);
	root = temp;
}

void r(node*& root)
{
	node* temp = root->left;
	root->left = temp->right;
	temp->right = root;
	updataheight(root);
	updataheight(temp);
	root = temp;
}

void insert(node*& root, int v)
{
	if (root == NULL)
	{
		root = newnode(v);
		return;
	}
	if (v < root->v)
	{
		insert(root->left, v);
		updataheight(root);
		if (getbalancefactor(root) == 2)
		{
			if (getbalancefactor(root->left) == 1)
				r(root);
			else if (getbalancefactor(root->left) == -1)
			{
				l(root->left);
				r(root);
			}
		}
	}
	else
	{
		insert(root->right, v);
		updataheight(root);
		if (getbalancefactor(root) == -2)
		{
			if (getbalancefactor(root->right) == -1)
				l(root);
			else if (getbalancefactor(root->right) == 1)
			{
				r(root->right);
				l(root);
			}
		}
	}
}

int main()
{
	int n, v;
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		cin >> v;
		insert(root, v);
	}
	cout << root->v << endl;
	return 0;
}