def evalInfixStack(expression):
""" Evaluate a fully parenthesized infix expression using a stack.
This function evaluates fully parenthesized expressions involving
single digit integers and the operators addition (+), subtraction (-),
multiplication (*), integer division (/), and modular division (%).
A BadExpressionError will be raised if the expression contains unrecognized
characters, or is not well formed. Spaces and tab characters are ignored.
Arguments: expression - a string containing a mathematical expression.
Returns: an integer containing the value of the expression.
"""
tempchar1 = ""
variables = Stack()
tempchar2 = expression.split()
characters = tempchar1.join(tempchar2)
print characters
for i in characters:
if not realNum(i) and i not in "+-%*/()":
raise BadExpressionError()
else:
if realNum(i) or i in "+-%*/":
variables.push(i)
if i is ')':
var2 = variables.pop()
op = variables.pop()
var1 = variables.pop()
value = evaluate(op, var1, var2)
variables.push(value)
return variables.peek()
print input
for ch in input:
if ch >= 'A' and ch <= 'Z':
output += ch
if ch == '(':
stack.push(ch)
if ch == ')':
while not stack.isEmpty():
cur = stack.pop()
if cur == "(":
break
output += cur
if ch in ('+', '-', '*', '/'):
while not stack.isEmpty():
if getpri(stack.peek()) >= getpri(ch):
output += stack.pop()
else:
break
stack.push(ch)
#if not stack.isEmpty():
#print "stack: "
#stack.show()
while not stack.isEmpty():
output += stack.pop()
print output
class RedBlackStack():
# Creates an empty red/black stack.
def __init__(self):
self.RBStack=Stack()
# Returns true if the red/black stack is empty of false otherwise.
def isEmpty(self):
return (self.RBStack.isEmpty())
# Returns the number of items in the stack.
def __len__(self):
return len(self.RBStack)
# Pushes a node that stores item and color onto top of stack.
def push(self, item, color):
tmpColor=color.lower()
assert(tmpColor=='r' or tmpColor=='b' or tmpColor=='black' or tmpColor=='red'),"Invalid color"
tmpNode=_Node(item,color)
self.RBStack.push(tmpNode)
# Removes the last node placed on top of stack based on input color, and returns item.
# If color is None, removes last node placed on stack and returns item.
def pop(self,color=None):
assert(not self.RBStack.isEmpty()),"Stack is Empty"
if (color==None):
return self.RBStack.pop().item
tmpColor=color.lower()
assert(tmpColor=='r' or tmpColor=='b' or tmpColor=='black' or tmpColor=='red'),"Invalid color"
if(tmpColor=='r' or tmpColor=='red'):
tmpStack=Stack()
while(not self.RBStack.isEmpty()):
tmpNode=self.RBStack.pop()
if (tmpNode.color=='r' or tmpNode.color=='red'):
while(not tmpStack.isEmpty()):
self.RBStack.push(tmpStack.pop())
return tmpNode.item
break
else:
tmpStack.push(tmpNode)
while(not tmpStack.isEmpty()):
self.RBStack.push(tmpStack.pop())
assert(False),"Color item not found."
else:
tmpStack=Stack()
while(not self.RBStack.isEmpty()):
tmpNode=self.RBStack.pop()
if (tmpNode.color=='b' or tmpNode.color=='black'):
while(not tmpStack.isEmpty()):
self.RBStack.push(tmpStack.pop())
return tmpNode.item
break
else:
tmpStack.push(tmpNode)
while(not tmpStack.isEmpty()):
self.RBStack.push(tmpStack.pop())
assert(False),"Color not found."
# Returns last item on stack based on color input without removing respected node.
# If color is None, returns last item placed on stack.
def peek(self,color=None):
assert(not self.RBStack.isEmpty()),"Stack is Empty"
if (color==None):
return self.RBStack.peek().item
tmpColor=color.lower()
assert(tmpColor=='r' or tmpColor=='b' or tmpColor=='black' or tmpColor=='red'),"Invalid color"
if(tmpColor=='r' or tmpColor=='red'):
tmpStack=Stack()
while(not self.RBStack.isEmpty()):
tmpNode=self.RBStack.peek()
if (tmpNode.color=='r' or tmpNode.color=='red'):
while(not tmpStack.isEmpty()):
self.RBStack.push(tmpStack.pop())
return tmpNode.item
break
else:
tmpStack.push(self.RBStack.pop())
while(not tmpStack.isEmpty()):
self.RBStack.push(tmpStack.pop())
assert(False),"Color item not found."
else:
tmpStack=Stack()
while(not self.RBStack.isEmpty()):
tmpNode=self.RBStack.peek()
if (tmpNode.color=='b' or tmpNode.color=='black'):
while(not tmpStack.isEmpty()):
self.RBStack.push(tmpStack.pop())
return tmpNode.item
break
else:
tmpStack.push(self.RBStack.pop())
while(not tmpStack.isEmpty()):
self.RBStack.push(tmpStack.pop())
assert(False),"Color not found."