Merge Three Sorted graphs
Last updated: October 10, 2025
Quick Overview
Given three sorted strings, merge them into a single sorted result.
Robinhood
October 10, 202529
11
4,296 solved
Given three sorted strings, merge them into a single sorted result.
This coding problem is frequently asked during Phone Screen at Robinhood. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Robinhood 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 you parallelize this solution?
- What happens if the input contains duplicates?
- How would your solution change if the input was sorted?
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Practice DSA ProblemsSample Answer
Problem Analysis
To merge three sorted strings, we need to recognize that this problem can be approached using the Two Pointers technique. Each string can be treated as a sorted list of characters, and we can use ...
Approach
- Initialize three pointers,
i,j, andk, to 0. These will track our current position in each of the three input strings respectively. - Create an empty list
resultto store the merged chara...
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