Number of Islands

arraydepth-first searchbreadth-first search

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: 1

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

Constraints

m == grid.length

n == grid[i].length

1 <= m, n <= 300

grid[i][j] is '0' or '1' .

🤔

Medium

Difficulty

Topic Info

ModuleDSA

CategoryArray

Sub-topicDepth-First Search