Number of Islands

MediumPython

Problem

How would you solve the number of islands problem in a 2D grid?

Implement num_islands(grid), where grid is a rectangular list of lists containing only the strings '1' and '0'. Land cells are connected only horizontally or vertically, not diagonally. Return the number of distinct islands without changing the input grid.

Constraints

0 <= len(grid) <= 300
If grid is non-empty, every row has the same positive length
Each cell is either '0' or '1'
Connectivity is horizontal or vertical only
The input grid must not be modified

Function Signature

def num_islands(grid):

CodePython 3

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