Coding - Number of Islands I

Problem Statement

Number of Islands

Given a 2D grid grid where '1' represents land and '0' represents water, count and return the number of islands.

An island is formed by connecting adjacent lands horizontally or vertically and is surrounded by water. You may assume water is surrounding the grid (i.e., all the edges are water).

Examples

1. 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

2. 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 <= 200
• grid[i][j] is '1' or '0'

Follow-up:**

• Could you solve this problem in O(n) time complexity with a specific algorithm design?

Hints

• Union Find Algorithm
• Depth-First Search (DFS)
• Breadth-First Search (BFS)

NOT_FOUND