Related Coding / DSA
Count Connected Land Regions in a Grid
Given a 2D grid of land and water cells, count the number of distinct connected land regions, where cells are connected horizontally or vertically.
1. Problem Statement
You are given a grid where each cell is empty (0), clean (1), or contaminated (2). Every minute, contamination spreads to horizontally or vertically adjacent clean cells. Return the minimum number of minutes for every clean cell to become contaminated, or -1 if some clean cell can never be reached.
2. Live Coding Format
Work in the provided coding workspace while explaining your decisions to the live interviewer. Validation may use inline tests, examples, comments, or a verbal walkthrough.
3. Key Focus Areas
- 1Problem clarification and contract
- 2Approach exploration and optimality
- 3Think-aloud communication and pacing
- 4Implementation correctness
- 5Code quality and language fluency
- 6Handwritten tests and dry run
- 7Debugging and self-correction
- 8Complexity analysis
- 9Follow-up performance
4. What Strong Candidates Should Demonstrate
- ✓Clarify cell states, spread direction rules, and impossible-case behavior before coding.
- ✓Explain a naive round-by-round full-grid rescan baseline and improve to a multi-source BFS.
- ✓Think aloud while implementing careful level-by-level traversal.
- ✓Validate with explicit expected outputs and a top-to-bottom handwritten dry run.
- ✓Analyze time and space complexity and handle a bounded follow-up modification.
Want interactive feedback?
Practice this problem in the live coding workspace while the interviewer probes your clarification, implementation, trade-offs, and validation.
Continue to DashboardCore Concepts
Grid TraversalMulti-Source BFSQueuesComplexity Analysis
Continue preparing
Build a complete software engineer mock interview plan
Prepare by company
Related Coding / DSA
Cheapest Route Within a Stop Limit
Given one-way routes between cities each with a cost, find the cheapest total cost from a source city to a destination city using at most k intermediate stops.
Related Coding / DSA
Count Contiguous Runs Summing to a Target
Given a sequence of integers (possibly negative) and a target sum, count how many contiguous subarrays sum exactly to the target.
Related Coding / DSA
Determine a Valid Course Completion Order
Given a number of courses and a list of prerequisite pairs, determine a valid order to complete all courses, or report that no valid order exists.