from collections import deque
def maybe_queue(row, col, game, q, seen):
"""
Add coordinate, (`row`, `col`), to the queue, `q`, as long as it exists in
the map, `game`, and it is not already present in `seen`.
"""
if row >= 0 and row < len(game) and col >= 0 and col < len(game[0]):
if game[row][col] == 'L' and (row, col) not in seen:
q.append((row, col))
def visit_island(row, col, game, seen):
"""
Starting at the coordinate, (`row`, `col`), in the map, `game`, visit all
surrounding tiles marked as land by adding them to the `seen` set.
"""
q = deque()
q.append((row, col))
while q:
row, col = q.popleft()
seen.add((row, col))
maybe_queue(row - 1, col, game, q, seen) # UP
maybe_queue(row + 1, col, game, q, seen) # DOWN
maybe_queue(row, col - 1, game, q, seen) # LEFT
maybe_queue(row, col + 1, game, q, seen) # RIGHT
def count_islands(game):
"""
Return the number of contiguous land tiles in the map, `game`.
"""
result = 0
seen = set()
for row in range(len(game)):
for col in range(len(game[row])):
if game[row][col] == 'L' and (row, col) not in seen:
visit_island(row, col, game, seen)
result += 1
return result
################################################################################
# Tests
################################################################################
game = [
"LWLWWW",
"LLLWWW",
"WWWLLW",
]
result = count_islands(game)
print(result)
assert result == 2
print("Success!")
