Optimize inversion for without recursion
Last updated: August 18, 2025
Quick Overview
Given a binary tree, write a function to invert the tree (swap the left and right children of all nodes) without using recursion. The function should take the root node of the tree as input and return the root of the inverted tree.
Grubhub
August 18, 202526
14
3,805 solved
Given a binary tree, write a function to invert the tree (swap the left and right children of all nodes) without using recursion. The function should take the root node of the tree as input and return the root of the inverted tree.
Grubhub uses this problem in the Technical 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
- What happens if the input contains duplicates?
- Can you solve this in a single pass?
- What is the worst-case input for your solution?
Sharpen Your Skills on Codemia
Practice similar problems with our interactive workspace, get AI feedback, and track your progress.
Practice DSA ProblemsSample Answer
Problem Analysis
The problem involves inverting a binary tree, which means swapping the left and right children of every node. The specific pattern that applies here is Breadth-First Search (BFS) or **Level Order ...
Approach
- Initialize a Queue: Start with a queue and enqueue the root node of the binary tree.
- Iterate While Queue is Not Empty: While there are nodes in the queue:
- Dequeue the front node. ...
Submit Your Answer
