rotation on Binary Tree
Last updated: August 13, 2025
Quick Overview
Given a binary tree, implement a function to rotate the tree to the right by 90 degrees. The function should take the root node of the binary tree as input and return the new root node after the rotation. Ensure that the structure of the tree is maintained and that the output reflects the correct orientation of the nodes post-rotation.
Optiver
August 13, 2025124
11
2,914 solved
Given a binary tree, implement a function to rotate the tree to the right by 90 degrees. The function should take the root node of the binary tree as input and return the new root node after the rotation. Ensure that the structure of the tree is maintained and that the output reflects the correct orientation of the nodes post-rotation.
This coding problem is frequently asked during Technical Screen at Optiver. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Optiver 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 solve this in a single pass?
- Can you solve this iteratively instead of recursively (or vice versa)?
- What happens if the input contains duplicates?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem involves rotating a binary tree to the right by 90 degrees. This can be solved using a recursive approach where we need to rearrange the pointers of the nodes. The main pattern here is tre...
Approach
- Base Case: If the root is
None, returnNone. - Recursion: For each node, perform the following:
- Store the left child in a temporary variable.
- Recursively rotate the left chil...
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