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maze.py
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maze.py
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class Node():
def __init__(self, state, parent, action, cost=0):
self.state = state
self.parent = parent
self.action = action
self.cost = cost
class StackFrontier():
def __init__(self):
self.frontier = []
def add(self, node):
self.frontier.append(node)
def contains_state(self, state):
return any(node.state == state for node in self.frontier)
def empty(self):
return len(self.frontier) == 0
def remove(self):
if self.empty():
raise Exception("Empty Frontier")
else:
node = self.frontier[-1]
self.frontier = self.frontier[:-1]
return node
class QueueFrontier(StackFrontier):
def remove(self):
if self.empty():
raise Exception("Empty Frontier")
else:
node = self.frontier[0]
self.frontier = self.frontier[1:]
return node
class GreedyBestFirst(StackFrontier):
def remove(self):
if self.empty():
raise Exception("Empty Frontier")
else:
lowestnode = self.frontier[0]
for node in self.frontier:
if node.cost < lowestnode.cost:
lowestnode = node
self.frontier.pop(self.frontier.index(lowestnode))
return lowestnode
class Astar(StackFrontier):
def remove(self):
if self.empty():
raise Exception("Empty Frontier")
else:
lowestnode = self.frontier[0]
for node in self.frontier:
if node.cost < lowestnode.cost:
lowestnode = node
self.frontier.pop(self.frontier.index(lowestnode))
return lowestnode
class DFSMaze:
def __init__(self, filename):
with open(filename) as f:
contents = f.read()
if contents.count("A") != 1:
raise Exception("Maze must have a start point")
if contents.count("B") != 1:
raise Exception("Maze must have a goal")
contents = contents.splitlines()
self.height = len(contents)
self.width = max(len(line) for line in contents)
self.walls = []
for i in range(self.height):
row = []
for j in range(self.width):
try:
if contents[i][j] == "A":
self.start = (i, j)
row.append(False)
elif contents[i][j] == "B":
self.goal = (i, j)
row.append(False)
elif contents[i][j] == " ":
row.append(False)
else:
row.append(True)
except IndexError:
row.append(False)
self.walls.append(row)
self.solution = None
f.close()
def neighbors(self, state):
row, col = state
candidates = [
("up", (row - 1, col)),
("down", (row + 1, col)),
("left", (row, col - 1)),
("right", (row, col + 1))
]
result = []
for action, (r, c) in candidates:
if 0 <= r < self.height and 0 <= c < self.width and not self.walls[r][c]:
result.append((action, (r, c)))
return result
def solve(self):
self.num_explored = 0
start = Node(state = self.start, parent = None, action = None)
frontier = StackFrontier()
frontier.add(start)
self.explored = []
while True:
if frontier.empty():
raise Exception ("No solution")
node = frontier.remove()
self.num_explored += 1
if node.state == self.goal:
self.explored.append(node.state)
actions = []
cells = []
while node.parent is not None:
actions.append(node.action)
cells.append(node.state)
node = node.parent
actions.reverse()
cells.reverse()
self.solution = (actions, cells)
return
self.explored.append(node.state)
for action, state in self.neighbors(node.state):
if not frontier.contains_state(state) and state not in self.explored:
child = Node(state=state, parent=node, action=action)
frontier.add(child)
class BFSMaze(DFSMaze):
def solve(self):
self.num_explored = 0
start = Node(state = self.start, parent = None, action = None)
frontier = QueueFrontier()
frontier.add(start)
self.explored = []
while True:
if frontier.empty():
raise Exception ("No solution")
node = frontier.remove()
self.num_explored += 1
if node.state == self.goal:
self.explored.append(node.state)
actions = []
cells = []
while node.parent is not None:
actions.append(node.action)
cells.append(node.state)
node = node.parent
actions.reverse()
cells.reverse()
self.solution = (actions, cells)
return
self.explored.append(node.state)
for action, state in self.neighbors(node.state):
if not frontier.contains_state(state) and state not in self.explored:
child = Node(state=state, parent=node, action=action)
frontier.add(child)
class GreedyBestFirstMaze(DFSMaze):
def determineCost(self, node):
#heuristic function
node.cost = abs(node.state[0] - self.goal[0]) + abs(node.state[1] - self.goal[1])
def solve(self):
self.num_explored = 0
start = Node(state = self.start, parent = None, action = None)
frontier = GreedyBestFirst()
frontier.add(start)
self.explored = []
while True:
if frontier.empty():
raise Exception ("No solution")
for node in frontier.frontier:
self.determineCost(node)
node = frontier.remove()
self.num_explored += 1
if node.state == self.goal:
self.explored.append(node.state)
actions = []
cells = []
while node.parent is not None:
actions.append(node.action)
cells.append(node.state)
node = node.parent
actions.reverse()
cells.reverse()
self.solution = (actions, cells)
return
self.explored.append(node.state)
for action, state in self.neighbors(node.state):
if not frontier.contains_state(state) and state not in self.explored:
child = Node(state=state, parent=node, action=action)
frontier.add(child)
class AstarMaze(DFSMaze):
def determineCost(self, node):
#heuristic function
h = abs(node.state[0] - self.goal[0]) + abs(node.state[1] - self.goal[1])
#cost to reach node
g = 0
parent = node.parent
while parent is not None:
parent = parent.parent
g += 1
node.cost = h + g
def solve(self):
self.num_explored = 0
start = Node(state = self.start, parent = None, action = None)
frontier = Astar()
frontier.add(start)
self.explored = []
while True:
if frontier.empty():
raise Exception ("No solution")
for node in frontier.frontier:
self.determineCost(node)
node = frontier.remove()
self.num_explored += 1
if node.state == self.goal:
self.explored.append(node.state)
actions = []
cells = []
while node.parent is not None:
actions.append(node.action)
cells.append(node.state)
node = node.parent
actions.reverse()
cells.reverse()
self.solution = (actions, cells)
return
self.explored.append(node.state)
for action, state in self.neighbors(node.state):
if not frontier.contains_state(state) and state not in self.explored:
child = Node(state=state, parent=node, action=action)
frontier.add(child)