def check_goal(sn, problem):
#take a SearchNode as an argument. If the SearchNode is the goal, return the path from the start node to goal node.
if problem.goal_test(sn.state):
path = []
stack = Stack()
stack.push(sn.action)
while sn.parent != None:
stack.push(sn.parent.action)
sn = sn.parent
while not stack.is_empty():
path.append(stack.pop())
return path[1:]
else:
return None
def check_goal(sn, problem):
if problem.goal_test(sn.state):
path = []
stack = Stack()
stack.push(sn.action)
while sn.parent != None:
stack.push(sn.parent.action)
sn = sn.parent
while not stack.is_empty():
path.append(stack.pop())
return path[1:]
else:
return None
def solve(problem):
""" *** YOUR CODE HERE *** """
# util.raise_not_defined() #Remove this line when you have implemented BrFS
stack = Stack()
depth_limit = 0
s0 = problem.get_initial_state()
sn_root = SearchNode(s0)
# depth += 1
check = None
while True:
explored = []
explored.append(s0)
stack = Stack()
stack.push(sn_root)
while not stack.is_empty():
# print("here")
# check_limit = stack.peek()
frontier = stack.pop()
# if depth_limit != 0:
# print(str(frontier.action) + " "+ str(frontier.depth))
check = check_goal(frontier, problem)
if check != None:
return check
else:
if (frontier.depth == depth_limit):
continue
for successor, action, cost in problem.get_successors(
frontier.state):
# if successor != frontier.state:
if successor not in explored:
explored.append(successor)
sn = SearchNode(successor, action, cost, frontier,
frontier.depth + 1)
# if stack.find(sn)
stack.push(sn)
depth_limit += 1
print(depth_limit)
print(" ")
def dls(problem, limit):
# *** YOUR CODE HERE ***
frontiers = Stack()
s0 = problem.get_initial_state()
#initiate the frontier by the start point
#state,action,cost,parent,depth
a = SearchNode(s0)
frontiers.push(a)
while not frontiers.is_empty():
cur = frontiers.pop()
#goal_test
if problem.goal_test(cur.state):
return route(cur)
if cur.depth != limit:
#add frontiers
for successor, action, cost in problem.get_successors(cur.state):
b = SearchNode(successor, action, cur.path_cost + cost, cur,
cur.depth + 1)
if valid_node(b):
frontiers.push(b)
def solve(problem):
""" *** YOUR CODE HERE *** """
# util.raise_not_defined() #Remove this line when you have implemented BrFS
depth_limit = 0
s0 = problem.get_initial_state()
sn_root = SearchNode(s0)
check = None
while True:
frontier = Stack()
frontier.push(sn_root)
while not frontier.is_empty():
current_node = frontier.pop()
#check if this node is the goal or not
check = check_goal(current_node, problem)
if check != None: #if check != None: reached goal, so "check" contains the path
return check
else:
if (current_node.depth == depth_limit):
continue
for successor, action, cost in problem.get_successors(
current_node.state):
# if the successor is not explored yet, append this new successor to the explored dictionary
tmp = current_node
flag = True
while tmp.parent != None:
if successor == tmp.parent.state:
flag = False
break
tmp = tmp.parent
if flag:
sn = SearchNode(successor, action, cost, current_node,
current_node.depth + 1)
frontier.push(sn)
print("depth limit = " + str(depth_limit))
depth_limit += 1
def dls_search(problem, depth_limit):
# The frontier is a Stack (defined in frontiers.py), for its LIFO queuing policy.
frontier = Stack()
# Use SearchNode (defined in search_strategies.py) as the class of elements in frontier, and initialize frontier.
frontier.push(SearchNode(problem.get_initial_state()))
explored = [] # The closed list (of nodes already explored).
while not frontier.is_empty():
# Check the first node in frontier.
node = frontier.pop()
if problem.goal_test(node.state): return node
if node.depth == depth_limit: continue
for point in explored[::]:
if point.depth > node.depth:
explored.remove(point)
# Expand this node if it is not the goal, nor does it reach the depth_limit.
for successor, action, cost in problem.get_successors(node.state):
# Avoid revisiting the explored states.
if successor in [x.state for x in explored]:
continue
else:
new_node = SearchNode(state=successor,
action=action,
path_cost=node.path_cost + cost,
parent=node,
depth=node.depth + 1)
# Add the successor node to frontier and explored.
frontier.push(new_node)
explored.append(new_node)
else:
print(depth_limit)
return 'cutoff'