Number of Islands via Graph Traversal

Problem

Count the islands in a grid of string cells, where 1 is land and 0 is water.

An island is a maximal group of land cells connected horizontally or vertically (4-connectivity). Return the number of islands; an empty grid has 0.

Hint

Flood fill from every unvisited land cell and increment the counter.

case 1

in: [[["1","1","0"],["1","0","0"],["0","0","1"]]]

expected: 2

case 2

in: [[["1","1"],["1","1"]]]

expected: 1

case 3

in: [[["0","0"],["0","0"]]]

expected: 0

case 4

in: [[]]

expected: 0

case 5

in: [[["1"]]]

expected: 1

Starter codePython

def num_islands(grid):
    # Your code here
    pass

5 test cases · run your code against them in the editor