Problem Set
#10
Number of Islands
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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.
Examples
Example 1
Input:
grid = [
["1","1","1","1","0"],
["1","1","0","1","0"],
["1","1","0","0","0"],
["0","0","0","0","0"]
]Output:
1Explanation:
All '1's are connected together horizontally or vertically, forming a single island.
Example 2
Input:
grid = [
["1","1","0","0","0"],
["1","1","0","0","0"],
["0","0","1","0","0"],
["0","0","0","1","1"]
]Output:
3Explanation:
There are 3 isolated islands.
Constraints
m == grid.lengthn == grid[i].length1 <= m, n <= 300grid[i][j] is '0' or '1'.
Hints
1
2
3
4
5
6
7
8
9
10
Input (grid matrix):