Grid DFS Implementation | Dataford Interview Questions

Explain how you would implement a depth-first search on a grid and handle visited cells and boundaries.

Implement num_islands(grid), returning the number of four-directionally connected regions containing 1. Treat 0 as empty, do not count diagonal connections, and leave the input unchanged.

Input is a list of equally sized lists of integers. Return an integer. Return 0 for an empty grid.

Constraints

0 <= len(grid) <= 100
Each row has the same number of columns
0 <= len(grid[0]) <= 100 when the grid is non-empty
Each cell is either 0 or 1
Connections use only up, down, left, and right neighbors
The input grid must remain unchanged

Function Signature

def num_islands(grid):

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