Number of Islands
Detailed guide and Python implementation for the 'Number of Islands' problem.
Problem Statement
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.
Write a function numIslands(grid: List[List[str]]) -> int.
- •m == len(grid)
- •n == len(grid[i])
- •1 <= m, n <= 300
- •grid[i][j] is '0' or '1'
Examples
grid = [["1","1","1","1","0"],["1","1","0","1","0"],["1","1","0","0","0"],["0","0","0","0","0"]]
1
There is a single island consisting of all connected '1's starting from top-left.
grid = [["1","1","0","0","0"],["1","1","0","0","0"],["0","0","1","0","0"],["0","0","0","1","1"]]
3
There are three distinct islands separated by '0's.
Need a Hint?
Edge Cases to Watch
- Empty input structures
- Single element inputs
- Large numerical bounds
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