def postfix_verbose(string):
""" Evaluate the postfix string, using a stack.
Elements must be separated by spaces.
Display progress on screen.
"""
tokenlist = string.split()
stack = Stack()
for token in tokenlist:
print('next token taken from string is', token)
if token in ["+", "-", "*", "/"]:
second = stack.pop()
first = stack.pop()
print(' Op, so pop twice, and evaluate <2nd-top> <op> <top>',
first, token, second)
if token == "+":
print(' = ', first + second)
stack.push(first + second)
elif token == "-":
print(' = ', first - second)
stack.push(first - second)
elif token == "*":
print(' = ', first * second)
stack.push(first * second)
else:
print(' = ', first / second)
stack.push(first / second)
print(' and push back onto stack')
else:
print(' Value (=', token, ') so push onto stack')
stack.push(int(token))
print('Stack is now:', stack)
print('No tokens left in string, so pop from stack (of length 1):', stack)
return stack.pop()
def infixConverter(equationString):
numStack = Stack()
numList = []
# operatorValues = {"/":2, "*":2, "+":1, "-":1}
for variable in equationString:
try:
int(variable)
numList.append(variable)
except ValueError:
if variable == "(":
numStack.push(variable)
elif variable == ")":
while numStack.top() != "(":
numList.append(numStack.pop())
numStack.pop()
elif (variable == "*" or variable == "/"):
if numStack.top() == "*" or numStack.top() == "/":
numList.append(numStack.pop())
numStack.push(variable)
else:
numStack.push(variable)
elif (variable == "+" or variable == "-"):
numStack.push(variable)
while numStack.length() != 0:
numList.append(numStack.pop())
s = " "
print(s.join(numList))
def queue_reverser(queue):
new_queue = Queue()
stack = Stack()
length = queue.length
for _ in range(length):
item = queue.dequeue()
stack.push(item)
queue.enqueue(item)
for _ in range(length):
new_queue.enqueue(stack.pop())
return new_queue
def postfix(string):
""" Evaluate the postfix string, using a stack.
Elements must be separated by spaces.
"""
tokenlist = string.split()
stack = Stack()
for token in tokenlist:
if token in ["+", "-", "*", "/"]:
second = stack.pop()
first = stack.pop()
if token == "+":
stack.push(first + second)
elif token == "-":
stack.push(first - second)
elif token == "*":
stack.push(first * second)
else:
stack.push(first / second)
else:
stack.push(int(token))
return stack.pop()
def reverse_queue(queue):
""" Reverse a queue.
Note that this will destroy the original queue.
Args:
queue - a queue
Returns the reverse of the input queue.
"""
outqueue = QueueV3()
stack = Stack()
while not queue.length() == 0:
item = queue.dequeue()
stack.push(item)
print('dequeued', item)
while not stack.length() == 0:
item = stack.pop()
outqueue.enqueue(item)
print('enqueued', item)
return outqueue
def main():
print('stackReverser\n')
stack1 = Stack()
alpha = ['a', 'b', 'c', 'd', 'e']
alpha = [1, 2, 3]
for i in range(len(alpha)):
stack1.push(alpha[i])
rev_stack = stackReverser(stack1)
print(rev_stack)
for i in range(stack1.length()):
print(stack1.pop())
for i in range(rev_stack.length()):
print(rev_stack.pop())
print(rev_stack)
print('bracketChecker\n')
test_string = '[he{}ll(ooo)oooooo(o)]'
print(bracketChecker(test_string))
def reverse_queue2(queue):
""" Reverse a queue.
This will finish with the original queue in its original state.
Args:
queue - a queue
Returns the reverse of the input queue.
"""
outqueue = QueueV3()
stack = Stack()
i = queue.length()
for pos in range(i):
item = queue.dequeue()
stack.push(item)
print('dequeued', item)
queue.enqueue(item)
while not stack.length() == 0:
item = stack.pop()
outqueue.enqueue(item)
print('enqueued', item)
return outqueue
def palindrome_check_list(inlist):
""" Determine whether inlist is a palindrome, using a stack. """
size = len(inlist)
mid = size // 2
even = True
if size % 2 == 1:
even = False
print('Midpoint is', mid, '; inlist is of EVEN length:', even)
stack = Stack()
pos = 0
while pos < mid:
stack.push(inlist[pos])
pos = pos + 1
if not even:
pos = pos + 1
while pos < len(inlist):
print('mylist[', pos, ']=', inlist[pos], '; stack.top() =',
stack.top())
#if inlist[pos] != stack.pop():
if not inlist[pos].is_equal(stack.pop()):
return False
pos = pos + 1
return True
def correctBracket(givenString):
charStack = Stack()
for char in givenString:
if char == '{' or char == '[' or char == '(':
charStack.push(char)
elif char == '}':
if charStack.top() != '{':
return 'INCORRECT'
charStack.pop()
elif char == ']':
if charStack.top() != '[':
return 'INCORRECT'
charStack.pop()
elif char == ')':
if charStack.top() != '(':
return 'INCORRECT'
charStack.pop()
return 'ITS CORRECT'
def palindrome_check(string):
""" Determine whether string is a palindrome, using a stack. """
mylist = list(string)
size = len(mylist)
mid = size // 2
even = True
if size % 2 == 1:
even = False
print('Midpoint is', mid, '; string is of EVEN length:', even)
stack = Stack() #create and return a stack object
pos = 0
while pos < mid: #push first half of the string onto the stack
stack.push(mylist[pos])
pos = pos + 1
if not even:
pos = pos + 1
while pos < len(mylist): #now pop and compare the two half lists
print('mylist[', pos, ']=', mylist[pos], '; stack.top() =',
stack.top())
if mylist[pos] != stack.pop():
return False
pos = pos + 1
print('This is a palindrome')
return True
def bracketChecker(input_string):
open_brackets = ['(', '[', '{']
close_brackets = [')', ']', '}']
stack = Stack()
for char in input_string:
if char in open_brackets:
stack.push(char)
elif char in close_brackets:
if char == ')':
if stack.top() != '(':
return False
stack.pop()
elif char == ']':
if stack.top() != '[':
return False
stack.pop()
elif char == '}':
if stack.top() != '{':
return False
stack.pop()
return True