989. Number of Islands (DFS)

Given a 2D grid of 1s (land) and 0s (water), count the number of islands. An island is a maximal group of 1s connected horizontally or vertically. The input is JSON {grid}.

Input: JSON {grid}.

Output: Integer — the number of islands.

Examples

Input: {"grid":[[1,1,0,0],[1,0,0,1],[0,0,1,1]]}
Output: 2
Explanation: Two separate land masses.

Input: {"grid":[[0]]}
Output: 0
Explanation: All water.

Input: {"grid":[[1]]}
Output: 1
Explanation: One land cell.

Constraints

• 1<=rows,cols<=300
• cells are 0 or 1

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