1066 Root of AVL Tree (25分)

#include<cstdio>
#include<algorithm>
using namespace std;
struct node {
	int val, height;
	node *left, *right;
	node(int v) {
		val = v;
		height = 1;
		left = NULL;
		right = NULL;
	}
};
int getHeight(node *n) {
	return n == NULL ? 0 : n->height;
}
void updateHeight(node *root) {
	root->height = max(getHeight(root->left), getHeight(root->right)) + 1;
}
int getBalanceFactor(node *n) {
	return getHeight(n->left) - getHeight(n->right);
}
void R(node *&root) {
	node *temp = root->left;
	root->left = root->left->right;
	temp->right = root;
	root = temp;
	updateHeight(root->right);  //旋转完记得更新结点高度
	updateHeight(root);
}
void L(node *&root) {
	node *temp = root->right;
	root->right = root->right->left;
	temp->left = root;
	root = temp;
	updateHeight(root->left);
	updateHeight(root);
}
void insert(node * &root, int val) {
	if (root == NULL) {
		root = new node(val);
		return;
	}
	if (val < root->val) {	//插入到左子树中
		insert(root->left, val);
		updateHeight(root);
		if (getBalanceFactor(root) == 2) {
			if (getBalanceFactor(root->left) == 1) {	//右单旋
				R(root);
			}
			else if (getBalanceFactor(root->left) == -1) {	//左右双旋
				L(root->left);
				R(root);
			}
		}
	}
	else {
		insert(root->right, val);
		updateHeight(root);
		if (getBalanceFactor(root) == -2) {
			if (getBalanceFactor(root->right) == -1) {	//左单旋
				L(root);
			}
			else if (getBalanceFactor(root->right) == 1) {	//右左双旋
				R(root->right);
				L(root);
			}
		}
	}
}
int main() {
	int n;
	scanf("%d", &n);
	node *root = NULL;
	for (int i = 0;i < n;i++) {
		int temp;
		scanf("%d", &temp);
		insert(root, temp);
	}
	printf("%d", root->val);
}