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"Algorithm, you are A*" solution in Clear category for Open Labyrinth by siebenschlaefer
import collections
import heapq
def checkio(maze_map):
"""Return the shortest path from (1, 1) to (10, 10) in 'maze_map'."""
Point = collections.namedtuple("Point", ("x", "y"))
directions = (
("N", Point(0, -1)),
("S", Point(0, +1)),
("W", Point(-1, 0)),
("E", Point(+1, 0)))
goal = Point(10, 10)
return "".join(a_star_search(
start=Point(1, 1),
is_goal=lambda state: state == Point(10, 10),
next_moves=lambda state: (
(move, 1, Point(state.x + step.x, state.y + step.y))
for move, step in directions
if maze_map[state.y + step.y][state.x + step.x] == 0),
heuristic=lambda state: manhattan_distance(state, goal))[0])
def manhattan_distance(a, b):
return abs(a.x - b.x) + abs(a.y - b.y)
def a_star_search(*, start, is_goal, next_moves, heuristic):
"""Compute the cheapest path using the A* search algorithm.
Keyword arguments:
start -- the start state
is_goal -- function (state -> bool)
returns True iff the goal is reached.
next_moves -- function (state -> (move, cost, state))
returns all possible moves/states from the given state
heuristic -- function (state -> cost)
returns an estimate of the cost from state to goal.
must never overestimate the real cost
Returns:
A list of moves of the shortest path and its cumulated cost.
state must be hashable, cost must be numeric.
"""
Trace = collections.namedtuple(
"Trace", ("cost", "last_state", "last_move"))
pqueue = [(heuristic(start), start)]
best_so_far = {start: Trace(cost=0, last_state=None, last_move=None)}
while pqueue:
_, state = heapq.heappop(pqueue)
cost = best_so_far[state].cost
if is_goal(state):
break
for move, move_cost, new_state in next_moves(state):
new_cost = cost + move_cost
best = best_so_far.get(new_state)
if best and best.cost <= new_cost:
continue
best_so_far[new_state] = Trace(
cost=new_cost, last_state=state, last_move=move)
heapq.heappush(pqueue, (
new_cost + heuristic(new_state),
new_state))
else:
raise ValueError("no path found")
path = []
while best_so_far[state].last_state is not None:
path.append(best_so_far[state].last_move)
state = best_so_far[state].last_state
path.reverse()
return path, cost
if __name__ == '__main__':
#This code using only for self-checking and not necessary for auto-testing
def check_route(func, labyrinth):
MOVE = {"S": (1, 0), "N": (-1, 0), "W": (0, -1), "E": (0, 1)}
#copy maze
route = func([row[:] for row in labyrinth])
pos = (1, 1)
goal = (10, 10)
for i, d in enumerate(route):
move = MOVE.get(d, None)
if not move:
print("Wrong symbol in route")
return False
pos = pos[0] + move[0], pos[1] + move[1]
if pos == goal:
return True
if labyrinth[pos[0]][pos[1]] == 1:
print("Player in the pit")
return False
print("Player did not reach exit")
return False
# These assert are using only for self-testing as examples.
assert check_route(checkio, [
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
[1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1],
[1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1],
[1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1],
[1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 1, 1],
[1, 0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 1],
[1, 0, 1, 0, 0, 1, 1, 1, 1, 1, 0, 1],
[1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1],
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]]), "First maze"
assert check_route(checkio, [
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
[1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]]), "Empty maze"
assert check_route(checkio, [
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
[1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1],
[1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 1],
[1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1],
[1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1],
[1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1],
[1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 1],
[1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1],
[1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1],
[1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1],
[1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 1],
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]]), "Up and down maze"
assert check_route(checkio, [
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
[1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1],
[1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1],
[1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1],
[1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1],
[1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1],
[1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1],
[1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1],
[1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1],
[1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1],
[1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1],
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]]), "Dotted maze"
assert check_route(checkio, [
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
[1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1],
[1, 0, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1],
[1, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1],
[1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1],
[1, 1, 1, 1, 1, 1, 0, 1, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 1, 1, 1, 0, 1, 1, 1],
[1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1],
[1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1],
[1, 0, 1, 0, 1, 0, 1, 1, 0, 0, 0, 1],
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]]), "Need left maze"
assert check_route(checkio, [
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
[1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1],
[1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1],
[1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1],
[1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1],
[1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1],
[1, 1, 1, 1, 1, 0, 1, 0, 0, 1, 0, 1],
[1, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1],
[1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1],
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]]), "The big dead end."
print("The local tests are done.")
Aug. 1, 2015
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