def infix_to_postfix(infix_expr):
precedence = {}
precedence["*"] = 3
precedence["/"] = 3
precedence["+"] = 2
precedence["-"] = 2
precedence["("] = 1
op_stack = Stack()
postfix_list = []
token_list = infix_expr.split()
for token in token_list:
if token in "ABCDEFGHIJKLLMNOPQRSTUVWXYZ" or token in "0123456789":
postfix_list.append(token)
elif token == '(':
op_stack.push(token)
elif token == ')':
top_token = op_stack.pop()
while top_token != '(':
postfix_list.append(top_token)
top_token = op_stack.pop()
else:
while (not op_stack.is_empty()) and (precedence[op_stack.peek()] >= precedence[token]):
postfix_list.append(op_stack.pop())
op_stack.push(token)
while not op_stack.is_empty():
postfix_list.append(op_stack.pop())
return "".join(postfix_list)
def postfix_eval(postfix_expr):
operand_stack = Stack()
token_list = postfix_expr.split()
for token in token_list:
if token in "0123456789":
operand_stack.push(token)
else:
operand2 = operand_stack.pop()
operand1 = operand_stack.pop()
result = do_math(token, int(operand1), int(operand2))
operand_stack.push(result)
return operand_stack.pop()
def par_checker(symbol_string):
s = Stack()
balanced = True
index = 0
while index < len(symbol_string) and balanced:
symbol = symbol_string[index]
if symbol == '(':
s.push(symbol)
else:
if s.is_empty():
balanced = False
else:
s.pop()
index += 1
return balanced and s.is_empty()
def divide_by_2(dec_number):
rem_stack = Stack()
while dec_number > 0:
rem = dec_number % 2
rem_stack.push(rem)
dec_number //= 2 # // integer division
bin_string = ""
while not rem_stack.is_empty():
bin_string += str(rem_stack.pop())
return bin_string
def base_converter(dec_number, base):
rem_stack = Stack()
while dec_number > 0:
rem = dec_number % base
rem_stack.push(rem)
dec_number //= base # // integer division
base_string = ""
while not rem_stack.is_empty():
base_string += str(rem_stack.pop())
return base_string
def build_parse_tree(mathexp):
tokens = mathexp.split()
p_stack = Stack()
e_tree = BinaryTree('')
p_stack.push(e_tree)
curr = e_tree
for t in tokens:
if t == '(':
curr.insert_left('')
p_stack.push(curr)
curr = curr.get_left_child()
elif t not in ['+', '-', '*', '/', ')']:
curr.set_root_val(int(t))
curr = p_stack.pop()
elif t in ['+', '-', '*', '/']:
curr.set_root_val(t)
curr.insert_right('')
p_stack.push(curr)
curr = curr.get_right_child()
elif t == ')':
curr = p_stack.pop()
else:
raise ValueError
return e_tree
def par_checker(symbol_string):
s = Stack()
balanced = True
index = 0
while index < len(symbol_string) and balanced:
symbol = symbol_string[index]
if symbol in '([{':
s.push(symbol)
else:
if s.is_empty():
balanced = False
else:
top = s.pop()
if not matches(top, symbol):
balanced = False
index += 1
return balanced and s.is_empty()
def aStarSearch(prob): # A* search
pq = PriorityQueue() # hang doi uu tien
occ = {} # dung de kiem tra xem mot state co duoc expand chua
dist = {} # so luong step can de di tu start den cac node
traverse = {} # dung de truy vet
startState = prob.getStartState() # trang thai ban dau
start = startState.getPacmanPosition(
) # vi tri ban dau cua pacman, cung la vi tri cua S
dist[start] = 0 # so luong step can de di tu start den goal la 0
pq.push(start, prob.getScore(start))
top = 0 # khai bao bien lay top cua priority queue
while pq.isEmpty() is False: # lap cho den khi goal node duoc expand
top = pq.pop()
if prob.isGoalState(
top): # kiem tra xem co phai la trang thai ket thuc
break
if occ.get(top, 0) != 0: # kiem tra mot trang thai co duoc expand chua
continue
occ[top] = 1
successors = prob.getChilds(top)
for s in successors:
# Neu TH1) trang thai hien tai chua tung duoc explore ,
# hay TH2) duoc explore roi nhung chua duoc expand va so step moi
# nho hon so step cu de di duoc den trang thai nay
if (dist.get(s, -1) == -1) or (occ.get(s, 0) == 0
and dist[s] > dist[top] + 1):
dist[s] = dist[top] + 1
traverse[s] = top
pq.push(s, dist[s] + prob.getScore(s))
if prob.isGoalState(top) is False:
return -1
q = Stack(
) # Tu day cho den het function nay la de lay list cac step de di tu S den G
node = top
while traverse.get(node, -1) != -1:
q.push(node)
node = traverse[node]
q.push(node)
path = []
while q.isEmpty() is False:
top = q.pop()
path.append(top)
return path