Count connected land components in a grid

You are given a 2D grid of characters where:

• '1' represents land
• '0' represents water

A group of land cells forms an island if they are connected 4-directionally (up, down, left, right). Determine the number of islands in the grid.

Input

• grid : an m x n matrix of characters ( '0' or '1' ).

Output

• Return an integer: the number of islands.

Constraints

• 1 <= m, n <= 300
• grid[i][j] ∈ {'0','1'}

Notes

• Diagonal adjacency does not connect islands.
• You may modify the grid in-place if desired.