95. Number of Islands

Medium

Topics

Companies

Helpful tools to learn & understand

Visualize LogicActive Simulator

Watch key transitions, pointers, and variables update step-by-step.

Open

Check Solutions

Read clean, documented implementations across multiple patterns.

View Code

Thinkpad (Draw & Note)

Sketch diagrams on an infinite canvas and draft notes directly inline.

Draw

Example 1:

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

Output: 6

Explanation: There are six islands formed by the connected '1's.

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: two small islands and one larger island.

Example 3:

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

Output: 0

Explanation: There are no islands in the grid, as all cells are water.

Example 4:

Input: grid = [["1"]]

Output: 1

Explanation: A single land cell represents one island.

Example 5:

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

Output: 5

Explanation: Each '1' is separated by '0's, resulting in five distinct islands.

Constraints:

•
•
•
•

Time Complexity

O(m × n)

Space Complexity