inversion on Binary Tree
Last updated: July 9, 2025
Quick Overview
Given a binary tree, write a function to invert the tree, meaning that for every node, its left and right children are swapped. The function should take the root of the binary tree as input and return the root of the inverted binary tree.
Shopify
July 9, 2025143
7
3,617 solved
Given a binary tree, write a function to invert the tree, meaning that for every node, its left and right children are swapped. The function should take the root of the binary tree as input and return the root of the inverted binary tree.
Shopify uses this problem in the Phone Screen to evaluate your algorithmic thinking. They expect you to discuss multiple approaches, analyze trade-offs between them, and implement the optimal solution with clean, readable code.
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?
- What is the worst-case input for your solution?
- How would you test this solution thoroughly?
- What if the input doesn't fit in memory?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to invert a binary tree, which means for every node, we swap its left and right children. This is a classic tree manipulation problem that can be effectively solved using Depth...
Approach
- Recursive DFS Approach: We will use a recursive function that takes a node as input.
- Base Case: If the node is
None, we returnNone. - Swap Children: If the node is not `Non...
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