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Number of Islands
Given an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number of islands.
An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically (4-directional). You may assume all four edges of the grid are surrounded by water.
Note: cells are string "0" and "1", matching LeetCode's signature.
Examples
Constraints
- m == grid.length
- n == grid[i].length
- 1 <= m, n <= 300
- grid[i][j] is "0" or "1".
Preview Mode
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Your approach
- Pattern:Depth-First Search
- Time:O(N)
- Space:O(1)
Complete approach — pattern and complexity both named.
Coach
What you got right
You correctly matched the sorted input requirement and implemented a linear-time scan using two pointers.
Where it diverged
No divergence detected. The code correctly aligns with the stated approach.
Next attempt: focus on
Try solving related sliding window problems to build familiarity with two-pointer variants.
Signals
No signals fired — clean run, you stayed in flow.