# 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;
    }
};