Transform string to tree
Last updated: February 16, 2026
Quick Overview
Convert the given array to tree structure following the specified rules.
Shopify
February 16, 2026287
3
3,532 solved
Convert the given array to tree structure following the specified rules.
This coding problem is frequently asked during Phone Screen at Shopify. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Shopify 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
- How would your solution change if the input was sorted?
- How would you parallelize this solution?
- Can you solve this iteratively instead of recursively (or vice versa)?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires transforming an array into a tree structure based on specific rules. The key pattern here is the use of recursive tree construction. Each element of the array can be viewed as...
Approach
- Base Case: If the array is empty, return None as there are no nodes to form a tree.
- Recursive Function: Create a function
build_tree(arr, start, end)that constructs the tree:- Fin...
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