DFS on graph
Last updated: February 1, 2026
Quick Overview
Apply the Sliding Window algorithm on a grid to solve this optimization problem.
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Apply the Sliding Window algorithm on a grid to solve this optimization problem.
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
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
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?
- What if the input doesn't fit in memory?
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Practice DSA ProblemsSample Answer
Problem Analysis
Start by understanding the input/output format and constraints. Identify the core problem pattern. Ask clarifying questions: Is the input sorted? Can ...
Brute Force Approach
Always start with the simplest correct solution, even if it's not optimal. This shows you can solve the problem and gives you a baseline to optimize f...
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