def runDFS():
initial_state = Problem.CREATE_INITIAL_STATE()
print("Initial State:")
print(Problem.DESCRIBE_STATE(initial_state))
global COUNT, BACKLINKS
COUNT = 0
BACKLINKS = {}
IterativeDFS(initial_state)
print(str(COUNT) + " states examined.")
def backtrace(S):
global BACKLINKS
path = []
while not S == -1:
path.append(S)
S = BACKLINKS[Problem.HASHCODE(S)]
path.reverse()
print("Solution path: ")
for s in path:
print(Problem.DESCRIBE_STATE(s))
return path
def IterativeAStar(initial_state):
global COUNT, BACKLINKS
OPEN = [initial_state]
CLOSED = []
BACKLINKS[Problem.HASHCODE(initial_state)] = -1
distance = {Problem.HASHCODE(initial_state): 0}
while OPEN != []:
S = OPEN[0]
del OPEN[0]
CLOSED.append(S)
if Problem.GOAL_TEST(S):
print(Problem.GOAL_MESSAGE_FUNCTION(S))
backtrace(S)
return
COUNT += 1
if (COUNT % 32)==0:
print(".",end="")
if (COUNT % 128)==0:
print("COUNT = "+str(COUNT))
print("len(OPEN)="+str(len(OPEN)))
print("len(CLOSED)="+str(len(CLOSED)))
L = []
for op in Problem.OPERATORS:
# Optionally uncomment the following when debugging
# a new problem formulation.
# print("Trying operator: "+op.name)
if op.precond(S):
new_state = op.state_transf(S)
if not occurs_in(new_state, CLOSED):
L.append(new_state)
BACKLINKS[Problem.HASHCODE(new_state)] = S
distance[Problem.HASHCODE(new_state)] = distance[Problem.HASHCODE(S)] + 1
# Uncomment for debugging:
print(Problem.DESCRIBE_STATE(new_state))
for s2 in L:
for i in range(len(OPEN)):
if Problem.DEEP_EQUALS(s2, OPEN[i]):
del OPEN[i]; break
OPEN = L + OPEN
OPEN = sorted(OPEN, key=lambda state: sort(state) + distance[Problem.HASHCODE(state)])
