Number of islands

Medium

You're given a m x n 2D grid of 1s and 0s, where 1 represents land and 0 represents water, find the number of islands that exist in the grid.

Consider an island as a group of adjacent 1s.

Adjancent cells are cells that are in either 4 directions - left, right, down, or up.

For example, given the following grid

grid = [
    [1, 0, 0],
    [0, 1, 1],
    [0, 1, 0]
]

Your function should return 2.

Try it

Before you look at the solution, try to code it yourself.

def num_islands(grid: list[list[int]]) -> int:
    # implement num_islands
    return -1

1def num_islands(grid: list[list[int]]) -> int:
2    # implement num_islands
3    return -1
4

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