# 思路

以 recursive 遍歷判斷 tree 是否高度平衡

# 參考程式碼

	/**
	* Definition for a binary tree node.
	* struct TreeNode {
	* int val;
	* TreeNode *left;
	* TreeNode *right;
	* TreeNode() : val(0), left(nullptr), right(nullptr) {}
	* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
	* TreeNode(int x, TreeNode left, TreeNode right) : val(x), left(left), right(right) {}
	* };
	*/

	static auto fast_io = []
	{
	ios::sync_with_stdio(false);
	cout.tie(nullptr);
	cin.tie(nullptr);
	return 0;
	}();

	class Solution {
	public:
	bool isBalanced(TreeNode* root)
	{
	if (!root) return true;
	if (abs(findHeight(root->left) - findHeight(root->right)) > 1) return false;
	return isBalanced(root->left) && isBalanced(root->right);
	}

	int findHeight(TreeNode* node)
	{
	if (!node) return 0;
	return max(findHeight(node->left), findHeight(node->right)) + 1;
	}
	};