LeetCode #200 - Number of Islands

Given a 2-dimensional grid consisting of '1's (land) and '0's (water), count 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.

Problem Statement

def numIslands(grid: List[List[str]]) -> int:

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: 1
Explanation: There is one island with connecting land cells.

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: 3
Explanation: There are three islands separated by water.

Constraints

• M == grid.length


• N == grid[i].length


• 1 <= M, N <= 300


• grid[i][j] is '0' or '1'.