leetcode - Balanced Binary Tree

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 depth of the two subtrees of every node never differ by more than 1.

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */struct TreeNode{int val;TreeNode *left;TreeNode *right;TreeNode(int x) : val(x), left(NULL), right(NULL) {}};class Solution {public:    bool isBalanced(TreeNode *root) {        if(root == NULL) return true;if(std::abs(dfs(root->left) - dfs(root->right)) > 1) return false;return isBalanced(root->left) && isBalanced(root->right);    }private:int dfs(TreeNode *root){if(root == NULL) return 0;return std::max(dfs(root->left),dfs(root->right)) + 1;}};