Number of Islands | Dataford Interview Questions

Number of Islands

Asked in the Round 1 technical stage. Explained BFS and DFS with complexity.

Task

Given a rectangular grid containing "1" for land and "0" for water, return the number of islands. An island is a group of horizontally or vertically adjacent land cells.

Implement num_islands(grid) and return an integer. Do not count diagonal adjacency. The input may be empty.

Constraints

0 <= rows, columns <= 300
The grid is rectangular when it is non-empty
Each cell is either "0" or "1"
Horizontal and vertical adjacency count, diagonal adjacency does not

Function Signature

def num_islands(grid):

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Problem