110

110. Balanced Binary Tree (Easy)

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.

 

Example 1:

Input: root = [3,9,20,null,null,15,7]
Output: true

Example 2:

Input: root = [1,2,2,3,3,null,null,4,4]
Output: false

Example 3:

Input: root = []
Output: true

 

Constraints:

• The number of nodes in the tree is in the range [0, 5000].
• -104 <= Node.val <= 104

Companies:
Amazon, Google, Facebook, Spotify

Related Topics:
Tree, Depth-First Search, Binary Tree

Similar Questions:

• Maximum Depth of Binary Tree (Easy)

Solution 1.

// OJ: https://leetcode.com/problems/balanced-binary-tree/
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(H)
class Solution {
private:
    bool isBalanced(TreeNode* root, int &h) {
        h = 0;
        if (!root) return true;
        int L = 0, R = 0;
        bool b = isBalanced(root->left, L) && isBalanced(root->right, R) && abs(L - R) <= 1;
        h = 1 + max(L, R);
        return b;
    }
public:
    bool isBalanced(TreeNode* root) {
        int h;
        return isBalanced(root, h);
    }
};