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breadth_first_search_3.py
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breadth_first_search_3.py
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# Sample code from https://www.redblobgames.com/pathfinding/a-star/
# Copyright 2014 Red Blob Games <[email protected]>
#
# Feel free to use this code in your own projects, including commercial projects
# License: Apache v2.0 <http://www.apache.org/licenses/LICENSE-2.0.html>
import collections
class SquareGrid:
def __init__(self, width, height):
self.width = width
self.height = height
self.walls = []
def in_bounds(self, id):
(x, y) = id
return 0 <= x < self.width and 0 <= y < self.height
def passable(self, id):
return id not in self.walls
def neighbors(self, id):
(x, y) = id
results = [(x + 1, y), (x, y - 1), (x - 1, y), (x, y + 1)]
if (x + y) % 2 == 0: results.reverse() # aesthetics
results = filter(self.in_bounds, results)
results = filter(self.passable, results)
return results
class Queue:
def __init__(self):
self.elements = collections.deque()
def empty(self):
return len(self.elements) == 0
def put(self, x):
self.elements.append(x)
def get(self):
return self.elements.popleft()
from implementation import *
def breadth_first_search_3(graph, start, goal):
frontier = Queue()
frontier.put(start)
came_from = {}
came_from[start] = None
while not frontier.empty():
current = frontier.get()
if current == goal:
break
for next in graph.neighbors(current):
if next not in came_from:
frontier.put(next)
came_from[next] = current
return came_from
def draw_tile(graph, id, style, width):
r = "."
if 'number' in style and id in style['number']: r = "%d" % style['number'][id]
if 'point_to' in style and style['point_to'].get(id, None) is not None:
(x1, y1) = id
(x2, y2) = style['point_to'][id]
if x2 == x1 + 1: r = ">"
if x2 == x1 - 1: r = "<"
if y2 == y1 + 1: r = "v"
if y2 == y1 - 1: r = "^"
if 'start' in style and id == style['start']: r = "A"
if 'goal' in style and id == style['goal']: r = "Z"
if 'path' in style and id in style['path']: r = "@"
if id in graph.walls: r = "#" * width
return r
def draw_grid(graph, width=2, **style):
for y in range(graph.height):
for x in range(graph.width):
print("%%-%ds" % width % draw_tile(graph, (x, y), style, width), end="")
print()
# utility functions for dealing with square grids
def from_id_width(id, width):
return id % width, id // width
# data from main article
DIAGRAM1_WALLS = [from_id_width(id, width=30) for id in
[21, 22, 51, 52, 81, 82, 93, 94, 111, 112, 123, 124, 133, 134, 141, 142, 153, 154, 163, 164, 171, 172,
173, 174, 175, 183, 184, 193, 194, 201, 202, 203, 204, 205, 213, 214, 223, 224, 243, 244, 253, 254,
273, 274, 283, 284, 303, 304, 313, 314, 333, 334, 343, 344, 373, 374, 403, 404, 433, 434]]
g = SquareGrid(30, 15)
g.walls = DIAGRAM1_WALLS
parents = breadth_first_search_3(g, (8, 7), (17, 2))
draw_grid(g, width=2, point_to=parents, start=(8, 7), goal=(17, 2))