// https://leetcode.com/problems/balanced-binary-tree/submissions/1292988627/
/**
 * Definition for a binary tree node.
 */
#include <algorithm>
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) {}
  };

class Solution {
public:
    bool isBalanced(TreeNode* root) {
        if (root == nullptr) return true;
        return std::abs(height(root->left) - height(root->right)) < 2 && isBalanced(root->left) && isBalanced(root->right);
    }

    int height(TreeNode* root) {
        if (root == nullptr) return 0;
        return (root->val = 1 + std::max(height(root->left), height(root->right)));
    }
};