Problem Statement

Given a 2D array (i.e., a matrix) containing only 1s (land) and 0s (water), count the number of islands in it.

An island is a connected set of 1s (land) and is surrounded by either an edge or 0s (water). Each cell is considered connected to other cells horizontally or vertically (not diagonally).

Example 1

Input: matrix =

Output: 1
Explanation: The matrix has only one island. See the highlighted cells below.

Example 2

Input: matrix =

Output: 3
Explanation: The matrix has three islands. See the highlighted cells below.

Constraints:

• m == matrix.length
• n == matrix[i].length
• 1 <= m, n <= 300
• matrix[i][j] is '0' or '1'.

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