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🔥Number of Islands: 2D Grid BFS/DFSMedium
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MediumTrees & Graphs•Acceptance: 58.9%

Number of Islands: 2D Grid BFS/DFS

Targeted in FAANG & Tech OA:AmazonGoogleMicrosoftUber
Real-World Engineering Context
Computer vision connected-component labeling in satellite imaging, autonomous driving road segment detection, and medical tumor segmentation.
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. You may assume all four edges of the grid are all surrounded by water.

Sample Test Cases

Input: [[["1","1","1","1","0"],["1","1","0","1","0"],["1","1","0","0","0"],["0","0","0","0","0"]]]
Expected: 1
Input: [[["1","1","0","0","0"],["1","1","0","0","0"],["0","0","1","0","0"],["0","0","0","1","1"]]]
Expected: 3

Constraints

  • m == grid.length
  • n == grid[i].length
  • 1 <= m, n <= 300
  • grid[i][j] is "0" or "1".
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