Number of Islands | Dataford Interview Questions

Number of Islands

Asked in the Round 2 - DSA stage. Given a 2D grid of "1" values representing land and "0" values representing water, return the number of islands. An island is formed by horizontally or vertically adjacent land cells, and each island must be surrounded by water or the grid boundary.

Input and Output

Implement num_islands(grid). The input is a list of lists of strings. Return an integer count. Mark visited land cells so they are not counted again.

Constraints

0 <= rows, columns <= 300
Each cell is either "0" or "1"
Cells connect only horizontally or vertically
The function may modify the input grid

Function Signature

def num_islands(grid):

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Problem