def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
# Initialize frontier to just the starting position
start = Node(state=source, parent=None, action=None)
stack_frontier = StackFrontier()
queue_frontier = QueueFrontier()
stack_frontier.add(start)
queue_frontier.add(start)
# Count length in path for both technicks to determine the shortest one
stack_frontier_path = []
queue_frontier_path = []
#Keep looping until solution found
stack_frontier_path = search_frontier(stack_frontier, stack_frontier_path,
target)
queue_frontier_path = search_frontier(queue_frontier, queue_frontier_path,
target)
if len(stack_frontier_path) <= len(queue_frontier_path) and len(
stack_frontier_path) != 0:
return stack_frontier_path
elif len(queue_frontier_path) != 0:
return queue_frontier_path
else:
return None
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
# Initialize frontier to just the starting position
start = Node(star=source, movie=None, parent=None)
frontier = StackFrontier()
# Start our search with the source
frontier.add(start)
# Initialize an empty explored set
explored = set()
# Keep looping until solution found
while True:
# If nothing left in frontier, then no path
if frontier.empty():
return None
# Choose a node from the frontier
node = frontier.remove()
# Mark node as explored
explored.add(node.star)
# Add neighbors to frontier
for movie_id, person_id in neighbors_for_person(node.star):
if not frontier.contains_star(person_id) and person_id not in explored:
child = Node(star=person_id, movie=movie_id, parent=node)
# If node is the goal, then we have a solution
if person_id == target:
return generate_path(child)
frontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
start = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
frontier.add(start)
explored = set()
while True:
if frontier.empty():
raise Exception("no solution")
node = frontier.remove()
if node.state == target:
path = []
while node.parent is not None:
path.append((node.action, node.state))
node = node.parent
path.reverse()
return path
explored.add(node.state)
for action, state in neighbors_for_person(node.state):
if not frontier.contains_state(state) and state not in explored:
child = Node(state=state, parent=node, action=action)
frontier.add(child)
def shortest_path(source, target):
start = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
frontier.add(start)
explored = set()
if source == target:
actions = [(start.action, target)]
while True:
if frontier.empty():
return None
current_node = frontier.remove()
explored.add(current_node.state)
for movie_id, person_id in neighbors_for_person(current_node.state):
if person_id not in explored and not frontier.contains_state(
person_id):
if person_id == target:
target_node = Node(state=person_id,
parent=current_node,
action=movie_id)
actions = []
while target_node.parent is not None:
actions.append((target_node.action, target_node.state))
target_node = target_node.parent
actions.reverse()
return actions
else:
frontier.add(
Node(state=person_id,
parent=current_node,
action=movie_id))
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
start = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
frontier.add(start)
nodesexplored = set()
while True:
if frontier.empty():
return None
node = frontier.remove()
if source == target:
solutions = []
while node.parent is not None:
solutions.append((node.action, node.state))
solutions.reverse()
return solutions
for movie_id, person_id in neighbors_for_person(node.state):
if not (person_id in nodesexplored):
child = Node(person_id, node, movie_id)
frontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
# TODO
# Keep track of number of states explored
num_explored = 0
# Initialize frontier to just the starting position
start = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
frontier.add(start)
# Initialize an empty explored set
explored = set()
# Keep looping until solution found
while True:
# If nothing left in frontier, then no path
if frontier.empty():
raise Exception("no solution")
# Choose a node from the frontier
node = frontier.remove()
num_explored += 1
# If node is the goal, then we have a solution
if node.state == target:
person_id = []
movie_id = []
while node.parent is not None:
person_id.append(node.state)
movie_id.append(node.action)
node = node.parent
movie_id.reverse()
person_id.reverse()
solution = []
solution = tuple(zip(movie_id, person_id))
return list(solution)
# Mark node as explored
explored.add(node.state)
# Add neighbors to frontier
for action, state in neighbors_for_person(node.state):
if not frontier.contains_state(state) and state not in explored:
child = Node(state=state, parent=node, action=action)
frontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
# path = []
# for current_elem in neighbors_for_person(source):
# movie_id = current_elem[0]
# person_id = current_elem[1]
# if person_id == target:
# path.append([movie_id, person_id])
# elif movie_id not in movies and person_id not in people:
# current_path = shortest_path(person_id, target)
# if current_path is not None:
# path.append(current_path)
# if len(path) == 0:
# return None
# return path
start = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
frontier.add(start)
explored = set()
while True:
if frontier.empty():
return None
node = frontier.remove()
if node.state == target:
# actions = []
# cells = []
# while node.parent is not None:
# actions.append(node.action)
# cells.append(node.state)
# node = node.parent
# actions.reverse()
# cells.reverse()
# return actions, cells
solution = []
while node.parent is not None:
solution.append((node.action,node.state))
node = node.parent
solution.reverse()
return solution
explored.add(node.state)
for action, state in neighbors_for_person(node.state):
if not frontier.contains_state(state) and state not in explored:
child = Node(state=state, parent=node, action=action)
frontier.add(child)
def shortest_path(source, target):
"""Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target."""
num_explored = 0
# Initialise frontier to the starting position
start_movieid = people[source]["movies"]
start = Node(state=source, parent=None, action=start_movieid)
end_movieid = people[target]["movies"]
end = Node(state=target, parent=None, action=end_movieid)
frontier = StackFrontier()
frontier.add(start)
# Initilize an empty emplored set
explored = set()
# Loop till solution is found
while True:
#If no possible path, returns None.
if frontier.empty():
raise Exception("no solution")
# Choose a node from the frontier
node = frontier.remove()
num_explored += 1
#If node is the goal, then solution found
solution = []
for movieid in end.action:
if movieid in node.action:
movie_person = set()
#Follow parent nodes to find solution
while node.parent:
personid = names[node.state]
movie_person = node.action, personid
node = node.parent
solution.append(movie_person)
solution.reverse()
return solution
# Mark node as explored
explored.add(node.state)
# Add neighbours to frontier
for movie_id, person_id in neighbors_for_person(names[node.state]):
if not frontier.contains_state(
person_id) and person_id not in explored:
child = Node(state=person_id, parent=node, action=movie_id)
frontier.add(child)
return solution
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
# Keep count of steps
num_explored = 0
# Initialize frontier to just the starting position
start = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
frontier.add(start)
# Initialize an empty explored set
explored = set()
# Keep looping until solution found
while True:
# If nothing left in frontier, then no path
if frontier.empty():
raise Exception("no solution")
# Choose a node from the frontier
node = frontier.remove()
num_explored += 1
# If node is the goal, then we have a solution
if node.state == target:
actions = []
cells = []
while node.parent is not None:
actions.append(node.action)
cells.append(node.state)
node = node.parent
actions.reverse()
cells.reverse()
retVal = [
] # list of tuples [(movie_id, person_id),(movie_id, person_id),(movie_id, person_id)]
for i in range(len(actions)):
retVal.append((actions[i], cells[i]))
return retVal
# Mark node as explored
explored.add(node.state)
# Add neighbors to frontier
for action, state in neighbors_for_person(node.state):
if not frontier.contains_state(state) and state not in explored:
child = Node(state=state, parent=node, action=action)
frontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
# Keep track of steps
num_of_steps = 0
# Initialize frontier to initial_node
initial_node = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
frontier.add(initial_node)
# Make new explored set
explored = set()
while True:
# Return no path if frontier empty
if frontier.empty():
raise Exception("no solution")
# Remove a node to explore
node = frontier.remove()
num_of_steps += 1
# If node is goal, make the path
if node.state == target:
cells = []
actions = []
while node.parent is not None:
cells.append(node.state)
actions.append(node.action)
node = node.parent
cells.reverse()
actions.reverse()
answer = []
for x in range(len(actions)):
answer.append((actions[x], cells[x]))
return answer
# Mark node as explored
explored.add(node.state)
for action, state in neighbors_for_person(node.state):
if not action or not state:
return None
elif not frontier.contains_state(state) and state not in explored:
child = Node(state=state, parent=node, action=action)
frontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
# Initialize frontier to just the starting position
start = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
frontier.add(start)
# Initialize an empty explored set
explored = set()
# Keep looping until solution found
while True:
# If nothing left in frontier, then no path
if frontier.empty():
raise Exception("no solution")
# Choose a node from the frontier
node = frontier.remove()
# If node is the goal, then we have a solution
if node.state == target:
moviess = []
actors = []
while node.parent is not None:
moviess.append(node.action)
actors.append(node.state)
node = node.parent
moviess.reverse()
actors.reverse()
solution = []
for i in range(len(moviess)):
solution.append((moviess[i], actors[i]))
return solution
# Mark node as explored
explored.add(node.state)
# Add neighbors to frontier
for movie_id, person_id in neighbors_for_person(node.state):
if not frontier.contains_state(
person_id) and person_id not in explored:
child = Node(state=person_id, parent=node, action=movie_id)
frontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
# Initialize frontier to just the starting position
start = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
frontier.add(start)
solution = []
# Initialize an empty explored set
explored = set()
# Keep looping until solution found
while True:
# If nothing left in the frontier, then no path
if frontier.empty():
return None
node = frontier.remove()
# Look at neighbors
for action, state in neighbors_for_person(node.state):
if not frontier.contains_state(state) and state not in explored:
child = Node(state=state, parent=node, action=action)
frontier.add(child)
if node.state == target:
actions = []
cells = []
while node.parent is not None:
actions.append(node.action)
cells.append(node.state)
node = node.parent
actions.reverse()
cells.reverse()
for i in range(0, len(actions)):
solutions += [(actions[i], state[i])]
return solutions
if child.state == target:
path = []
while child.parent is not None:
path.append((child.action, child.state))
child = child.parent
path.reverse()
return path
explored.add(node.state)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
Credit: adapted from CS50AI's maze.solve() function
"""
# Initialize frontier to just the starting position
start = Node(state=source, parent=None, action=None)
# Use breadth-first search to find shortest path
frontier = StackFrontier()
frontier.add(start)
# Initialize an empty explored set
explored = set()
# Keep looping until solution found
while True:
# If nothing left in frontier, then no path
if frontier.empty():
return None
# Choose a node from the frontier
node = frontier.remove()
# Mark node as explored
explored.add(node.state)
# Add neighbors to frontier
for movie, person in neighbors_for_person(node.state):
if not frontier.contains_state(person) and person not in explored:
child = Node(state=person, parent=node, action=movie)
# If node is the goal, then we have a solution
if child.state == target:
path = []
while child.parent is not None:
path.append((child.action, child.state))
child = child.parent
path.reverse()
return path
# Otherwise add node to the frontier
else:
frontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
# Initialize an empy frontier of the type specified at the top
# of the module
if SEARCH_TYPE == "DepthFirst":
frontier = StackFrontier()
elif SEARCH_TYPE == "BreadthFirst":
frontier = QueueFrontier()
else:
raise Exception("Illegal search type")
initialState = Node((None, source), None, None) # Starting node/person
frontier.add(
initialState) # Add the starting person id (source) to frontier
exploredSet = set() # Store explored nodes
# Search for the end state/person until no more nodes to explore
# meaning there is no path to from start node to end node
while not frontier.empty():
# Remove the current node from the frontier and add it to the
# exploredSet
currentNode = frontier.remove()
exploredSet.add(currentNode.state)
# Get neighbors of current node and add to frontier
neighbors = neighbors_for_person(currentNode.state[1])
for neighbor in neighbors:
if neighbor[1] == target:
endNode = Node(neighbor, currentNode, None)
return getSolutionPath(endNode)
if not frontier.contains_state(neighbor) and (neighbor
not in exploredSet):
neighborNode = Node(neighbor, currentNode,
None) # TODO what is an action
frontier.add(neighborNode)
return None # No solution found
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
#Initialize a BFS.
frontier = StackFrontier()
frontier.add(Node(state=source,parent=None,action=None))
#Setup the explored section
explored = set()
#Until a solution is found
while True:
#If the frontier is empty and no solution is found then there is no connection between the source and target.
if frontier.empty():
raise Exception("No Valid Solution")
#Extract a node from the frontier.
node = frontier.remove()
#If the node's person_id matches the id of the target the solution has been found.
if node.state == target:
movies = []
names = []
while node.parent is not None:
movies.append(node.action)
names.append(node.state)
node = node.parent
movies.reverse()
names.reverse()
solution = []
i = 0
while i < len(movies):
solution.append((movies[i],names[i]))
i += 1
return solution
#Add the explored node to the explored set after exploring it.
explored.add(node.state)
#Find the movies that the actor has played in and what other actors are in those movies.
for movie, name in neighbors_for_person(node.state):
if not frontier.contains_state(name) and name not in explored:
frontier.add(Node(state=name,parent=node,action=movie))
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
frontier = StackFrontier()
start = Node(state=source,parent=None,action=None)
solution = set()
explored = set()
frontier.add(start)
while True:
if frontier.empty() :
raise Exception("No solution")
node = frontier.remove()
sourceNeighbors = neighbors_for_person(node.state)
explored.add(node.state)
for movie,person in sourceNeighbors :
if target == person and node.state==source :
solution.add((movie,source))
solution.add((movie,person))
return solution
elif target == person and node.state != source :
movieperson = []
while node.parent is not None:
movieperson.append((node.action,node.state))
movieperson.reverse()
solution = movieperson
return solution
else:
if not frontier.contains_state(person) and person not in explored:
frontier.add(Node(state=person,parent=node,action=movie))
def shortest_path(source, target):
num_explored = 0
start = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
frontier.add(start)
explored = set()
while True:
if frontier.empty():
raise Exception("no solution")
node = frontier.remove()
num_explored += 1
if target == node.state:
actions = []
states = []
result = []
while node.parent is not None:
actions.append(node.action)
states.append(node.state)
node = node.parent
actions.reverse()
states.reverse()
for action, state in zip(actions, states):
result.append((action, state))
return result
explored.add(node.state)
for action, state in neighbors_for_person(node.state):
if not frontier.contains_state(state) and state not in explored:
child = Node(state=state, parent=node, action=action)
frontier.add(child)
raise NotImplementedError
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
Num_explored = 0
start = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
frontier.add(start)
explored = set()
while True:
if frontier.empty():
raise Exception("no solution)")
node = frontier.remove()
Num_explored += 1
print(Num_explored)
if node.state == target:
print("here is solution")
solution = []
while node.parent is not None:
solution.append((node.action, node.state))
print("getting ready...\n")
node = node.parent
return solution
explored.add(node.state)
for movie, state in neighbors_for_person(node.state):
if not frontier.contains_state(state) and state not in explored:
child = Node(state=state, parent=node, action=movie)
frontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
if source == target:
return None
num_explored_states = 0
start = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
frontier.add(start)
explored = set()
while True:
if frontier.empty():
return None
node = frontier.remove()
num_explored_states += 1
explored.add(node.state)
for action, state in neighbors_for_person(node.state):
if not frontier.contains_state(state) and state not in explored:
child = Node(state=state, parent=node, action=action)
if child.state == target:
movie_list = []
people_path = []
while child.parent is not None:
movie_list.append(child.action)
people_path.append(child.state)
child = child.parent
movie_list.reverse()
people_path.reverse()
return list(zip(movie_list, people_path))
frontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
sourcempid = list(neighbors_for_person(source)) #(movieId, personId), returns a set
start = Node(state = source,parent=None,action=None) #start.state gives the person id
stackFrontier = StackFrontier()
stackFrontier.add(start)
explored = set()
while True:
#checks if frontier is empty
if stackFrontier.empty():
return None
#removes the node while storing it into node
node = stackFrontier.remove()
explored.add(node.state)
#Add other personId to frontier
for tup in list(neighbors_for_person(node.state)):
if not stackFrontier.contains_state(tup[1]) and tup[1] not in explored:
child = Node(state=tup[1], parent=node, action=tup[0])
if child.state == target: #checks if the movies match
cells = []
while child.parent is not None:
cells.append((child.action,child.state))
child = child.parent
cells.reverse()
return cells
else:
stackFrontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
# Initialize frontier to just the starting position
start = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
# frontier = QueueFrontier()
frontier.add(start)
# Keep track of number of states explored
num_explored = 0
# Initialize an empty explored set
exploreds = set()
# keep looping until solution found
while True:
# if nothing left in frontier there is no path
if frontier.empty():
return None
# Remove a node from the frontier
node = frontier.remove()
num_explored += 1
# if node is the target, return the solution
if node.state == target:
solutions = []
# Follow parent nodes to find path
while node.parent is not None:
solutions = [(node.action, node.state)] + solutions
node = node.parent
return solutions
else:
# Add the node to the explored set
exploreds.add(node.state)
# Add neighbors to frontier
neighors = neighbors_for_person(node.state)
for action, state in neighors:
if not frontier.contains_state(
state) and state not in exploreds:
child = Node(state=state, parent=node, action=action)
frontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
degrees = 0
start = Node(source, None, None, degrees)
frontier = StackFrontier()
frontier.add(start)
explored = set()
nodes_explored = 0
pairs = []
while True:
if frontier.empty():
return None
node = frontier.remove()
nodes_explored += 1
print("Inside degree:", node.degree, "Nodes explored:", nodes_explored)
if node.state == target:
actions = []
cells = []
while node.parent is not None:
actions.append(node.action)
cells.append(node.state)
node = node.parent
actions.reverse()
cells.reverse()
for i in range(len(actions)):
pairs.append((actions[i], cells[i]))
return pairs
explored.add(node.state)
for movie_id, person_id in neighbors_for_person(node.state):
if not frontier.contains_state(person_id) and person_id not in explored and node.degree < 6:
child = Node(state=person_id, parent=node, action=movie_id, degree=node.degree + 1)
frontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
# Initialize frontier to just the starting position ,
start = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
frontier.add(start)
# Initialize an empty explored set
explored = set()
while True:
if frontier.empty():
raise Exception("no solution")
node = frontier.remove()
# Mark node as explored
explored.add(node.state)
# Add neighbors id for a given name to frontier
for movie_id, person_id in neighbors_for_person(node.state):
if not frontier.contains_state(
person_id) and person_id not in explored:
if person_id == target:
child = Node(state=person_id, parent=node, action=movie_id)
list_solution = []
while node.parent is not None:
list_solution.append((node.movie_id, node.person_id))
node = node.parent
list_solution.reverse()
return list_solution
else:
frontier.add(
Node(state=person_id, parent=node, action=movie_id))
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
myqueue = StackFrontier()
explored = set()
finalList = []
node = Node(source, None, None)
myqueue.add(node)
while (not myqueue.empty()):
node = myqueue.remove()
explored.add(node.state)
if node.state == target:
movies = []
stars = []
while node.parent != None:
finalList = []
movies.append(node.action)
stars.append(node.state)
node = node.parent
movies.reverse()
stars.reverse()
for i in range(len(movies)):
finalList.append((movies[i], stars[i]))
return finalList
for action, state in neighbors_for_person(node.state):
if action == None and state == None:
return None
else:
if state not in explored:
nei = Node(state, node.state, action)
myqueue.add(nei)
return None
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
# TODO
algo = 'BFS'
explored = set()
start = Node(source, parent=None, action=None)
frontier = QueueFrontier() if algo == 'BFS' else StackFrontier()
frontier.add(start)
# Keep looping until solution found
while True:
# If nothing left in frontier, then no path
if frontier.empty():
raise Exception("no solution")
# Choose a node from the frontier
node = frontier.remove()
# If node is the goal, then we have a solution
if node.state == target:
path = []
while node.parent is not None:
path.append((node.action, node.state))
node = node.parent
path.reverse()
return path
# Mark node as explored
explored.add(node.state)
# Add neighbors to frontier
for movie_id, person_id in neighbors_for_person(node.state):
if not frontier.contains_state(
person_id) and person_id not in explored:
child = Node(state=person_id, parent=node, action=movie_id)
if person_id == target:
frontier.seed(child)
else:
frontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
start = Node(source, None, None)
frontier = StackFrontier()
frontier.add(start)
explored = set()
while True:
if frontier == None:
raise Exception("None")
node = frontier.remove()
explored.add(node.state)
neighbors = neighbors_for_person(node.state)
for movie_id, person_id in neighbors:
if not frontier.contains_state(person_id) and person_id not in explored:
child = Node(person_id, node, movie_id)
if child.state == target:
path =[]
node = child
while node.parent is not None:
path.append((node.action, node.state))
node = node.parent
path.reverse()
return path
frontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
start = Node(source, None, None)
frontier = StackFrontier()
frontier.add(start)
explored = set()
while True:
if frontier.empty():
raise Exception("no solution")
node = frontier.remove()
if node == target:
return node
explored.add(node.state)
# TODO
raise NotImplementedError
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
import time
frontier = StackFrontier()
# frontier = QueueFrontier()
start = Node(state=source, action=None, parent=None, step=0)
frontier.add(start)
explored_nodes = dict()
explored_num = 0
solution = None
hit_count = dict()
start_time = time.time()
# List all options which step is 3 for Emma and Jeniffer
# solutions = []
while True:
if frontier.empty():
print("Hit count: ", hit_count)
print("Time cost: ", time.time() - start_time)
print("Num of explored nodes: ", explored_num)
return None if solution == None else solution[0]
# return None if len(solutions)==0 else solutions
node = frontier.remove()
# Explored {person_id:(step, movie_id)} is recorded
explored_nodes[node.state] = node.step
explored_num += 1
parent_id = node.state
for neighbor in neighbors_for_person(parent_id):
# If the person is 5 steps away (or even more) from the source, give it up because of Six Degrees of Kevin Bacon, and it can definitely improve the performance
if node.step > 5:
break
# If can find a shorter path/step than the explored (person_id, step) for the certain person, explore it, otherwise, give it up to improve performance
if neighbor[1] != parent_id and not frontier.contains_state(
neighbor[1]) and (
neighbor[1] not in explored_nodes.keys()
or node.step + 1 < explored_nodes[neighbor[1]]):
child = Node(state=neighbor[1],
action=neighbor[0],
parent=node,
step=node.step + 1)
if child.state == target:
step = child.step
# Recode the hit count for different steps/length of the path
if step in hit_count.keys():
hit_count[step] += 1
else:
hit_count[step] = 1
# Organize the being returned result via the node's parent link
links = []
while child.parent is not None:
links.append((child.action, child.state))
child = child.parent
links.reverse()
# Always fetch the shortest path if have.!!!!
if solution == None or solution[1] > step:
solution = (links, step)
# if step == 3:
# solutions.append(links)
# If the child is the target, not explore other neighbors any more.
break
else:
frontier.add(child)
def shortest_path(source, target):
"""
Returns the shortest list of (movie_id, person_id) pairs
that connect the source to the target.
If no possible path, returns None.
"""
# number of states explored
steps = 0
# create start node and initialize frontier
start = Node(state=source, parent=None, action=None)
frontier = StackFrontier()
# add start position to frontier
frontier.add(start)
# positions explored
explored = set()
# create loop to run until solution is found (or no solution)
while True:
# return error if no solution is found
if frontier.empty():
raise Exception("no solution")
# take last item added to list and increment number of steps by one
node = frontier.remove()
steps += 1
# if the target has been found, create lists to track pahtway for starts and associated movies
if node.state == target:
movies = []
stars = []
# work backwards until start state is reached, indicated by parent = None
while node.parent is not None:
movies.append(node.action)
stars.append(node.state)
node = node.parent
# reverse lists because we were starting with solution
movies.reverse()
stars.reverse()
# create a list of tuples to maintain association between movies and stars
solution = zip(movies, stars)
solution = list(solution)
# return solution
return solution
# if the solution hasn't been found, add node to the explored list
explored.add(node.state)
if not node.state == target:
# check all neighbors for the current node
for movie_id, person_id in neighbors_for_person(node.state):
# skip adding neighbors to the frontier if they are already there
if not frontier.contains_state(
person_id) and person_id not in explored:
# add neighbors to the frontier, documenting their person_id as the state, parent, as the current node and action as movie_id
child = Node(state=person_id, parent=node, action=movie_id)
frontier.add(child)
def __init__(self, grid_size, start, end, walls):
super().__init__(grid_size, start, end, walls)
self.frontier = StackFrontier()