###### tags: `leetcode`
# Question 110. Balanced Binary Tree
### Description:
Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as:

a binary tree in which the left and right subtrees of every node differ in height by no more than 1.

### Solution:
- DFS:
- find the depth of left and right subtree.
### AC code

/**
 * 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) {}
 * };
 */
class Solution {
public:
    int depth(TreeNode* root){
        if(root==NULL)
            return 0;
        return max(depth(root->left), depth(root->right))+1;        
    }
    
    bool isBalanced(TreeNode* root) {
        if(root==NULL)
            return true;
    
        int dl = depth(root->left);
        int dr = depth(root->right);
        if(abs(dl-dr)>1)
            return false;
        return isBalanced(root->left)&&isBalanced(root->right);
    }
};