inversion on Binary Tree
Last updated: July 3, 2025
Quick Overview
Given a binary tree, invert the tree by swapping the left and right children of all nodes. The function should return the root of the inverted binary tree. For example, if the input tree is represented as [4, 2, 7, 1, 3, 6, 9], the output should be the tree represented as [4, 7, 2, 9, 6, 3, 1].
Supabase
July 3, 2025230
15
2,011 solved
Given a binary tree, invert the tree by swapping the left and right children of all nodes. The function should return the root of the inverted binary tree. For example, if the input tree is represented as [4, 2, 7, 1, 3, 6, 9], the output should be the tree represented as [4, 7, 2, 9, 6, 3, 1].
This coding problem is frequently asked during Onsite at Supabase. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Supabase expects candidates to write production-quality code, not just solve the puzzle.
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
- Can you optimize the space complexity of your solution?
- How would you modify your solution to handle streaming input?
- What is the worst-case input for your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem of inverting a binary tree fits the pattern of a Depth First Search (DFS) traversal. In this case, we need to explore each node and swap its left and right children. The binary tree can be...
Approach
- Recursive DFS Approach:
- Start at the root of the tree.
- For each node, swap its left and right children.
- Recursively call the function for the left and right child nodes. -...
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