# CS50AI: Project 0: Degrees - Getting infinite loop

I am working on Project 0 for the CS50 AI Course and after finishing my function for shortest_path, I am getting an infinite loop(I added a counter that increments with print statements to be able to see the infinite loop in the output). I made sure that I only add neighbors to the frontier if they are not already in the frontier and have not been explored already, so I am not sure where this infinite loop is occurring from. Any help debugging would be appreciated. Here is the code:

``````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 = []

# 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 = QueueFrontier()

# Initialize an empty explored set
explored = set()

# Keep looping until solution found
counter = 0
while True:
print(counter)
counter += counter + 1
# If nothing left in frontier, then no path
if frontier.empty():
return None

# 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 = []
path=[]
while node.parent is not None:
#actions.append(node.action)
#cells.append(node.state)
path.append(node.action,node.state)
node = node.parent
#actions.reverse()
#cells.reverse()
path.reverse()
#solution = (actions, cells)
return path

# Mark node as explored