Island Perimeter

Problem

Given a grid of 0 water and 1 land cells, return the total perimeter around all land.

Each land cell contributes four edges, and every shared edge with the cell above or to the left removes two. Return 0 for empty or all-water grids.

Hint

Count each adjacency only once, using the top and left neighbours.

case 1

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

expected: 16

case 2

in: [[[1]]]

expected: 4

case 3

in: [[[1,0]]]

expected: 4

case 4

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

expected: 8

case 5

in: [[[0]]]

expected: 0

Starter codePython

def island_perimeter(grid):
    # Your code here
    pass

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