MEDIUM NC#82 Graphs / DFS
695. Max Area of Island
📖 Problem
You are given an m x n binary matrix grid where 0 represents water and 1 represents land. Find the maximum area of an island in grid. The island is connected by 4-directionally (horizontal or vertical) land cells.
🧠 Visual Learning Aid
1 Model the input into the right structure
2 Choose the core technique and invariant
3 Execute step-by-step with a sample
4 Validate complexity and edge cases
JS/TS Refreshers
- •Array methods (`push`, `pop`, `shift`, `slice`)
- •Object/Map/Set usage patterns
- •Function parameter and return typing
- •Recursive stack flow
- •Cycle prevention
- •Post-order reasoning
Logical Thinking Concepts
- •Define invariants before coding
- •Check edge cases first (`[]`, single element, duplicates)
- •Estimate time/space before implementation
- •Apply DFS reasoning pattern
- •Apply Recursion reasoning pattern
💡 Approach
- → Use DFS to explore each island
- → Track visited cells to avoid revisiting
- → Calculate area for each cell (current * future islands)
- → Keep track of maximum area seen
- → Time: O(m * n), Space: O(m * n) for recursion
🧭 Prerequisites
🛠️ Hints & Pitfalls
Hints
- •Use DFS to explore each island
- •Track visited cells to avoid revisiting
- •Calculate area for each cell (current * future islands)
Common Pitfalls
- •Keep track of maximum area seen
- •Time: O(m * n), Space: O(m * n) for recursion
🧪 Test Cases
Hidden tests on submit: 3
Test Case 1
Not run Input:
dfs(i, j, i + 1, 0); Expected:
Computed from hidden reference Test Case 2
Not run Input:
dfs(r: number, c: number, newColor: number); Expected:
Computed from hidden reference Test Case 3
Not run Input:
dfs(r - 1, c, newColor); Expected:
Computed from hidden reference 📝 Code Editor
📤 Output