Optimize partitioning for O(n) time

Last updated: February 10, 2026

Quick Overview

Find an efficient solution for rotation given the with follow-up constraint.

PlanetScale
Coding & Algorithms
Software Engineer
PlanetScale
February 10, 2026
Software Engineer
Phone Screen
Coding & Algorithms
Medium

10

7

864 solved


Find an efficient solution for rotation given the with follow-up constraint.

This coding problem is frequently asked during Phone Screen at PlanetScale. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. PlanetScale 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
Binary search and divide and conquer
Sorting and searching
Graph algorithms and traversal
Edge cases and input validation
Hash maps and frequency counting
Common algorithm patterns (sliding window, two pointers, BFS/DFS)
How to Approach This
  1. Clarify input constraints and edge cases before writing code.
  2. Walk through your approach verbally and confirm with the interviewer before coding.
  3. Start with a brute force solution, then optimize. Mention time and space complexity.
  4. Test your solution with examples, including edge cases like empty input or duplicates.
  5. Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
  • Can you solve this iteratively instead of recursively (or vice versa)?
  • How would you parallelize this solution?
  • What happens if the input contains duplicates?
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