What is the optimal time complexity of solving Balanced Binary Tree?

The optimized solution achieves a time complexity of O(n) by using sorting, mathematical shortcuts, or hash table lookups.

What is the auxiliary space complexity for Balanced Binary Tree?

The space complexity is O(1) since we only use a minimal/constant amount of extra memory for tracking variables (or auxiliary space if dynamic structures are allocated).

What are the typical edge cases we must handle in Balanced Binary Tree?

Key edge cases include empty collections, negative or large bounds causing integer overflow, arrays with only one element, or inputs where target criteria are not met.

How can we optimize the brute force approach for Balanced Binary Tree?

Brute force methods often inspect all possible combinations. We optimize this by sorting the input list to enable binary search, or tracking processed items in a set to avoid redundant nested loop lookups.

Back to Practice Dashboard

Top 150 InterviewMedium

Balanced Binary Tree

Learn how to solve the 'Balanced Binary Tree' problem. This detailed resource details brute force and optimized approaches.

Mode Selected

Problem Statement

Medium

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.

The tree is represented as a level-order list. Implement a function isBalanced(root: list) -> bool.

Constraints

•The number of nodes in the tree is in the range [0, 5000]
•-10000 <= Node.val <= 10000

Examples

Example 1

Input

[3,9,20,None,None,15,7]

Output

True

Explanation

The left subtree (rooted at 9) has depth 1, and the right subtree (rooted at 20) has depth 2. The difference is 1, so the tree is balanced.

Example 2

Input

[1,2,2,3,3,None,None,4,4]

Output

False

Explanation

The left subtree has depth 3 while the right subtree has depth 1. The difference is 2, so the tree is not balanced.

Example 3

Input

[]

Output

True

Explanation

An empty tree is considered balanced.

Need a Hint?

Perform a recursive tree traversal (DFS) or level-order traversal (BFS) using a queue/stack.

Edge Cases to Watch

Empty list or null input variables
Single item lists/arrays
Extremely large input bounds causing integer or stack overflow

Ready to Solve?

Open the problem in PyRun's browser-based Python editor. Your code runs fully offline — no server required.

Open in Editor