Balanced Binary Tree

Balanced Binary Tree

Given a binary tree, determine if it is height-balanced.

A height-balanced binary tree is a binary tree in which the depth of the two subtrees of every node never differs by more than one.

Examples

Example 1:

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

      3
     / \
    9  20
       / \
      15   7

Example 2:

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

         1
        / \
       2   2
      / \
     3   3
    / \
   4   4

Example 3:

Input: root = []
Output: true

Constraints

• The number of nodes in the tree is in the range [0, 5000].
• -10^4 <= Node.val <= 10^4

Expected Complexity

• Time: O(n)
• Space: O(h) where h is the height of the tree