Merge Three Sorted strings
Last updated: September 13, 2025
Quick Overview
Given k sorted binary trees, merge them into a single sorted result.
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Given k sorted binary trees, merge them into a single sorted result.
This coding problem is frequently asked during Phone Screen at Reddit. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Reddit 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?
- What if the input doesn't fit in memory?
- What happens if the input contains duplicates?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to merge three sorted binary trees into a single sorted result. This problem can be seen as a variant of the classic merging problem, typically tackled using a two-pointer tech...
Approach
- Initialize Pointers: Start by initializing a pointer for each of the three binary trees (let's call them
p1,p2,p3). These pointers will point to the current node being examined in each ...
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