inversion on Binary Tree
Last updated: July 31, 2025
Quick Overview
Given a binary tree, write a function to invert the tree, such that the left and right children of all nodes are swapped. The function should take the root node of the binary tree as input and return the root node of the inverted tree.
Brex
July 31, 202530
6
1,254 solved
Given a binary tree, write a function to invert the tree, such that the left and right children of all nodes are swapped. The function should take the root node of the binary tree as input and return the root node of the inverted tree.
Coding interviews at Brex focus on problem-solving approach as much as the final solution. The interviewer wants to see you break down the problem, consider edge cases, and optimize iteratively. Communication throughout the process is key.
What the Interviewer Expects
- Recognize the underlying problem pattern (sliding window, two pointers, BFS/DFS, etc.)
- Discuss multiple approaches and trade-offs before coding
- Implement an optimal solution with clean, production-quality code
- Handle all edge cases including boundary conditions and invalid input
- Optimize both time and space complexity with clear justification
- Test your solution systematically with well-chosen examples
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- How would your solution change if the input was sorted?
- How would you modify your solution to handle streaming input?
- What is the worst-case input for your solution?
- Can you solve this in a single pass?
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Problem Analysis
The problem requires us to invert a binary tree, which means swapping the left and right children of all nodes in the tree. This task can be efficiently approached using a Depth-First Search (DFS) str...
Approach
- Base Case: If the current node is
None, returnNone. This will handle leaf nodes and ensure we don't try to access properties of a non-existent node. - Swap Children: For the current n...
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