Optimize traversal for O(1) space
Last updated: December 1, 2025
Quick Overview
Given a binary tree, implement a traversal algorithm that visits all nodes while using O(1) space. You should return the values of the nodes in the order they are visited without using any additional data structures for storage. The traversal should be done iteratively, and the output should be a list of node values.
Splunk
December 1, 20254
9
1,945 solved
Given a binary tree, implement a traversal algorithm that visits all nodes while using O(1) space. You should return the values of the nodes in the order they are visited without using any additional data structures for storage. The traversal should be done iteratively, and the output should be a list of node values.
Splunk 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
- Can you solve this in a single pass?
- What is the worst-case input for your solution?
- How would you parallelize this solution?
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Problem Analysis
To solve the problem of traversing a binary tree with O(1) space, we can utilize the Morris Traversal algorithm, which allows us to achieve in-order traversal without using any additional data structu...
Approach
- Initialize a current pointer to the root of the tree.
- While the current pointer is not null, check if it has a left child.
- If it does, find the rightmost node in the left subtree (this will...
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