def distance_field(grid, position, obstacles):
"""
Compute a distance field on a grid in a given position,
with the given obstacles.
"""
boundary = Queue() # bsf uses queue dynamics
boundary.enqueue((position[0], position[1])) # put the starting grid in the queue
visited = [[EMPTY for _ in xrange(WIDTH)] for _ in xrange(HEIGHT)]
visited[position[0]][position[1]] = FULL # set the starting cell to visited
field = Grid(HEIGHT, WIDTH, STRMAP) # we'll store the distance field as a grid
field.set_all_to(-1) # -1 will symbolize unreachable cells
# Set obstacles
for obstacle in obstacles:
grid.set_obstacle(obstacle[0], obstacle[1])
field.set_obstacle(obstacle[0], obstacle[1])
field.set_empty(position[0], position[1]) # set the root position
while boundary: # while the queue is not empty
current = boundary.dequeue() # get a grid cell from the queue
neighbors = grid.four_neighbors(current[0], current[1]) # get the four neighbor cells:
# up, down, left, and right
for neighbor in neighbors: # for every neighbor cell
# If the cell hasn't been visited and has no obstacles:
if not visited[neighbor[0]][neighbor[1]] and grid.is_empty(neighbor[0], neighbor[1]):
visited[neighbor[0]][neighbor[1]] = FULL # set it as visited
boundary.enqueue(neighbor) # add it to the queue
field.set_to(neighbor[0], neighbor[1], # set the distance from the root
field.get_cell(current[0], current[1]) + 1)
return field
def bfs(grid, row, col):
"""
Perform a breath-first search in the given grid, starting
in the given cell.
"""
boundary = Queue() # bsf uses queue dynamics
boundary.enqueue((row, col)) # put the starting grid in the queue
visited = [[EMPTY for _ in xrange(WIDTH)] for _ in xrange(HEIGHT)]
visited[row][col] = FULL # set the starting cell to visited
while boundary: # while the queue is not empty
current = boundary.dequeue() # get a grid cell from the queue
grid.set_marked(current[0], current[1]) # (this is for the print)
neighbors = grid.four_neighbors(current[0], current[1]) # get the four neighbor cells:
print grid # up, down, left, and right
for neighbor in neighbors: # for every neighbor cell
if not visited[neighbor[0]][neighbor[1]]: # if it hasn't been visited
visited[neighbor[0]][neighbor[1]] = FULL # set it as visited
boundary.enqueue(neighbor) # add it to the queue
grid.set_full(neighbor[0], neighbor[1]) # (this is for the print)
print grid
