bomb_enemy.py

"""
Given a 2D grid, each cell is either a wall 'W',
an enemy 'E' or empty '0' (the number zero),
return the maximum enemies you can kill using one bomb.
The bomb kills all the enemies in the same row and column from
the planted point until it hits the wall since the wall is too strong
to be destroyed.
Note that you can only put the bomb at an empty cell.

Example:
For the given grid

0 E 0 0
E 0 W E
0 E 0 0

return 3. (Placing a bomb at (1,1) kills 3 enemies)
"""


def max_killed_enemies(grid):
    if not grid: return 0
    m, n = len(grid), len(grid[0])
    max_killed = 0
    row_e, col_e = 0, [0] * n
    # iterates over all cells in the grid
    for i in range(m):
        for j in range(n):
            # makes sure we are next to a wall.
            if j == 0 or grid[i][j - 1] == 'W':
                row_e = row_kills(grid, i, j)
            # makes sure we are next to a wall.
            if i == 0 or grid[i - 1][j] == 'W':
                col_e[j] = col_kills(grid, i, j)
            # makes sure the cell contains a 0
            if grid[i][j] == '0':
                # updates the variable
                max_killed = max(max_killed, row_e + col_e[j])

    return max_killed


# calculate killed enemies for row i from column j
def row_kills(grid, i, j):
    num = 0
    len_row = len(grid[0])
    while j < len_row and grid[i][j] != 'W':
        if grid[i][j] == 'E':
            num += 1
        j += 1
    return num


# calculate killed enemies for  column j from row i
def col_kills(grid, i, j):
    num = 0
    len_col = len(grid)
    while i < len_col and grid[i][j] != 'W':
        if grid[i][j] == 'E':
            num += 1
        i += 1
    return num


# ----------------- TESTS -------------------------

"""
    Testsuite for the project
"""

import unittest


class TestBombEnemy(unittest.TestCase):
    def test_3x4(self):
        grid1 = [["0", "E", "0", "0"],
                 ["E", "0", "W", "E"],
                 ["0", "E", "0", "0"]]
        self.assertEqual(3, max_killed_enemies(grid1))

    def test_4x4(self):
        grid1 = [
            ["0", "E", "0", "E"],
            ["E", "E", "E", "0"],
            ["E", "0", "W", "E"],
            ["0", "E", "0", "0"]]
        grid2 = [
            ["0", "0", "0", "E"],
            ["E", "0", "0", "0"],
            ["E", "0", "W", "E"],
            ["0", "E", "0", "0"]]
        self.assertEqual(5, max_killed_enemies(grid1))
        self.assertEqual(3, max_killed_enemies(grid2))


if __name__ == "__main__":
    unittest.main()