Number of Islands — Medium Coding Interview Question

Given an m x n 2D binary grid of '1's (land) and '0's (water), return the number of islands. An island is surrounded by water and formed by connecting adjacent lands horizontally or vertically.

Example

Input: grid = [["1","1","1","1","0"],["1","1","0","1","0"],["1","1","0","0","0"],["0","0","0","0","0"]]

Output: 1

Constraints

• 1 ≤ m, n ≤ 300

Topics & Companies

Topics: graphs, recursion

Asked by: Amazon, Google, Meta, Microsoft, Apple, Bloomberg, Uber

Optimal Solution Complexity

Time complexity: O(m×n). Space complexity: O(m×n).

Practice more

• All DSA Problems
• DSA Patterns