def IterativeDFS(initial_state):
global COUNT, BACKLINKS
OPEN = [initial_state]
CLOSED = []
BACKLINKS[Problem.HASHCODE(initial_state)] = -1
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
#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
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 Astar(initial_state):
global COUNT, BACKLINKS
OPEN = [initial_state]
CLOSED = []
BACKLINKS[Problem.HASHCODE(initial_state)] = -1
h_count = h_heuristics(initial_state)
g_score = {Problem.HASHCODE(initial_state): 0}
h_score = {Problem.HASHCODE(initial_state): h_count}
f_score = {Problem.HASHCODE(initial_state): h_count}
q = queue.PriorityQueue()
q.put(initial_state)
while OPEN != []:
S = OPEN[0]
prev_score = f_score[Problem.HASHCODE(S)]
for element in OPEN:
if f_score[Problem.HASHCODE(element)] < prev_score:
S = element
prev_score = f_score[Problem.HASHCODE(element)]
del OPEN[OPEN.index(S)]
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):
brand_new_state = new_state not in OPEN
lesser_score = False
if brand_new_state:
OPEN.append(new_state)
else:
lesser_score = g_score[Problem.HASHCODE(S)] <= g_score[
Problem.HASHCODE(new_state)]
if brand_new_state or lesser_score:
BACKLINKS[Problem.HASHCODE(new_state)] = S
new_state_hash = Problem.HASHCODE(new_state)
g_score[new_state_hash] = g_score[Problem.HASHCODE(
S)] + 1
h_score[new_state_hash] = h_heuristics(new_state)
f_score[new_state_hash] = g_score[Problem.HASHCODE(
new_state)] + h_score[Problem.HASHCODE(new_state)]
for s2 in L:
for i in range(len(OPEN)):
if Problem.DEEP_EQUALS(s2, OPEN[i]):
del OPEN[i]
break
