Number of Islands
mediumblind-75dsagraphsdfsmatrix
Asked at
Amazon, Google, LinkedIn, Meta, Microsoft
Problem statement
Implement numIslands for the classic Number of Islands problem.
This Blind 75 version is framed for frontend interviews: write clean JavaScript, name the invariant out loud, and handle edge cases without over-engineering.
What this tests
- Pattern:
grid DFS flood fill. - Ability to explain time and space complexity clearly.
- Careful handling of empty inputs, duplicates, and boundary cases.
- Production-style JavaScript readability, not just competitive-programming shortcuts.
Requirements & constraints
- Use JavaScript without external libraries.
- Prefer the standard optimal interview approach for this pattern.
- Return deterministic output when multiple valid outputs exist where the prompt implies ordering.
Examples
Example 1
Input: Use the canonical Blind 75 sample for this problem.
Output: Return the value required by the problem statement.
How to approach Number of Islands
The strategy an interviewer expects you to reach for.
Senior Frontend Approach Start by identifying the pattern: grid DFS flood fill. Then define the invariant the loop or recursion maintains before writing code.
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