This notebook was prepared by Donne Martin. Source and license info is on GitHub.

Challenge Notebook

Problem: Island Perimeter.

See the LeetCode problem page.

You are given a map in form of a two-dimensional integer grid where 1 represents land and 0 represents water. Grid cells are connected horizontally/vertically (not diagonally). The grid is completely surrounded by water, and there is exactly one island (i.e., one or more connected land cells). The island doesn't have "lakes" (water inside that isn't connected to the water around the island). One cell is a square with side length 1. The grid is rectangular, width and height don't exceed 100. Determine the perimeter of the island.

Example:

[[0,1,0,0],
 [1,1,1,0],
 [0,1,0,0],
 [1,1,0,0]]

Answer: 16

Constraints

  • Can we assume the inputs are valid?
    • No, check for None
  • Can we assume this fits memory?
    • Yes

Test Cases

* None -> TypeError
* [[1, 0]] -> 4
* [[0, 1, 0, 0],
   [1, 1, 1, 0],
   [0, 1, 0, 0],
   [1, 1, 0, 0]] -> 16

Algorithm

Refer to the Solution Notebook. If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start.

Code

In [ ]:
class Solution(object):

    def island_perimeter(self, grid):
        # TODO: Implement me
        pass

Unit Test

The following unit test is expected to fail until you solve the challenge.

In [ ]:
# %load test_island_perimeter.py
import unittest


class TestIslandPerimeter(unittest.TestCase):

    def test_island_perimeter(self):
        solution = Solution()
        self.assertRaises(TypeError, solution.island_perimeter, None)
        data = [[1, 0]]
        expected = 4
        self.assertEqual(solution.island_perimeter(data), expected)
        data = [[0, 1, 0, 0],
                [1, 1, 1, 0],
                [0, 1, 0, 0],
                [1, 1, 0, 0]]
        expected = 16
        self.assertEqual(solution.island_perimeter(data), expected)
        print('Success: test_island_perimeter')


def main():
    test = TestIslandPerimeter()
    test.test_island_perimeter()


if __name__ == '__main__':
    main()

Solution Notebook

Review the Solution Notebook for a discussion on algorithms and code solutions.