def invalidate(self):
"""
A boulder has been moved so the traceback must be recalculated.
"""
# calling this function means something has caused the old traceback to become invalid
self.traceback = None
# see where the boulders are
boulder_locations = [loc for loc, c in self.level.items() if c == '0']
# create solvers associated with boulder locations
pq = []
distance_solver_location_triples = []
for boulder_location in boulder_locations:
self.level[boulder_location] = '.'
boulder_transition = BoulderTransition(self, self.level, self.floor_neighbors, self.location_to_back_front_pairs)
boulder_heuristic = BoulderTransitionHeuristic(self, self.level, self.location_to_back_front_pairs)
initial_state = (boulder_location, self.player_location)
solver = AscDP.MeasureInformedTraceback([initial_state], boulder_transition, boulder_heuristic)
solver.step()
self.level[boulder_location] = '0'
distance = solver.get_distance()
if distance is not None:
heappush(pq, (distance, solver, boulder_location))
# Keep going until a solver has finished or until they have all failed to find a solution.
best_path = None
while pq:
distance, solver, boulder_location = heappop(pq)
solution = solver.get_solution()
if solution:
best_path = AscDP.traceback_to_path(*solution)
break
self.level[boulder_location] = '.'
solver.step()
self.level[boulder_location] = '0'
distance = solver.get_distance()
if distance is not None:
heappush(pq, (distance, solver, boulder_location))
# Set the path if one was found.
if best_path:
# Convert the path to boulder pushes.
assert len(best_path) > 1
self.traceback = []
for (new_boulder, new_player), (old_boulder, old_player) in zip(best_path[0:-1], best_path[1:]):
if new_boulder != old_boulder:
self.traceback.append((new_player, old_player))
