Merge K Sorted strings
Last updated: January 30, 2026
Quick Overview
Given two sorted arrays, merge them into a single sorted result.
PlanetScale
Coding & Algorithms
Software Engineer
PlanetScale
January 30, 2026Software Engineer
Phone Screen
Coding & Algorithms
Easy
143
10
3,180 solved
Given two sorted arrays, merge them into a single sorted result.
PlanetScale uses this problem in the Phone 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
- Identify the correct data structure and algorithm for the problem
- Write clean, bug-free code with proper variable naming
- Analyze time and space complexity correctly
- Handle basic edge cases (empty input, single element)
- Communicate your thought process while coding
Key Topics to Cover
Edge cases and input validation
Data structure selection and trade-offs
Common algorithm patterns (sliding window, two pointers, BFS/DFS)
Tree structures and recursion
Hash maps and frequency counting
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 test this solution thoroughly?
- What is the worst-case input for your solution?
- Can you solve this in a single pass?
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Practice DSA ProblemsSample Answer
Problem Analysis
To merge K sorted strings, we can utilize a min-heap (or priority queue) to efficiently combine the strings in sorted order. The min-heap allows us to always retrieve the smallest element among th...
Approach
- Initialize a min-heap: Start by creating a min-heap to store the first character from each string along with the string index and character index.
- Push initial elements: For each of th...
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