def infix_to_prefix(infix):
"""Converts given infix expression to postfix expression
using Shunting Yard Algorithm and converts that postfix to prefix"""
if infix == "":
return ""
#stack to temporarily store operators and paranthesis
stack = MyStack(size=len(infix) + 1)
postfix = [] # a list to store postifix expression
for char in infix:
if is_operand(char):
postfix.append(char)
elif char not in ['(', ')']:
while not stack.is_empty() and precedence(char) <= precedence(
stack.top()):
#Add elements from stack until stack is not empty and precedence of \n
#char is less than the top most stack element
postfix.append(stack.pop())
stack.push(char)
elif char == "(":
stack.push(char)
elif char == ")":
while not stack.is_empty() and stack.top() != "(":
postfix.append(stack.pop())
if stack.top() != "(":
raise ValueError("Parathesis Mismatch!")
stack.pop()
while not stack.is_empty():
# pop out and add all existing elements from stack and add in onto postfix
postfix.append(stack.pop())
stack.clear_stack()
# returns prefix string after converting the postfix passed to convert_to_prefix
return convert_to_prefix(postfix)
def push(self, value):
top = self.stack.peek()
if top.get_current_capacity() > 1:
top.push(value)
else:
self.stack.push(MyStack(self.capacity_per_stack))
self.stack.peek().push(value)
def __init__(self, degree):
# This method is complete.
self.degree = degree
self.rootNode = BTreeNode(degree)
# If time, file creation code, etc.
self.nodes = {}
self.stackOfNodes = MyStack()
self.rootNode.setIndex(1)
self.writeAt(1, self.rootNode)
self.rootIndex = 1
self.freeIndex = 2
def dequeue(self):
# Write your code here
temp_stack = MyStack()
while not self.main_stack.size() == 1:
temp_stack.push(self.main_stack.pop())
popped_item = self.main_stack.pop()
while not temp_stack.is_empty():
self.main_stack.push(temp_stack.pop())
return popped_item
def infix_to_postfix(infix):
"""Converts given infix expression to postfix expression
using Shunting Yard Algorithm"""
#stack to temporarily store operators and paranthesis
stack = MyStack(size= len(infix)+1)
postfix = [] # a list to store postifix expression
# Returns True if char is an operand
is_operand = lambda char: char.isalpha() or char.isnumeric()
# Returns the precedence of char from PRIORITY dict"""
PRIORITY = {"+": 1, "-": 1, "*": 2, "/": 2, "%": 2, "^": 3}
precedence = lambda char: PRIORITY[char] if char in PRIORITY else -1
for char in infix:
if is_operand(char):
postfix.append(char)
elif char not in ['(',')']:
while not stack.is_empty() and precedence(char) <= precedence(stack.top()):
#Add elements from stack until stack is not empty and precedence of \n
#char is less than the top most stack element
postfix.append(stack.pop())
stack.push(char)
elif char == "(":
stack.push(char)
elif char == ")":
while not stack.is_empty() and stack.top() != "(":
postfix.append(stack.pop())
if stack.top() != "(":
raise ValueError("Parathesis Mismatch!")
stack.pop()
while not stack.is_empty():
# pop out and add all existing elements from stack and add in onto postfix
postfix.append(stack.pop())
return " ".join(postfix)
"/": op.floordiv,
"+": op.add,
"-": op.sub,
}
def postfix_eval(postfix):
"""Return evaluated resultant of postfix"""
for item in postfix.split(" "):
if item.isdigit():
stack.push(item)
else:
temp_two = int(stack.pop())
temp_one = int(stack.pop())
stack.push(oper_dict[item](temp_one, temp_two))
return int(stack.top())
stack = MyStack()
def test_cases():
"""Sample test cases"""
assert postfix_eval('45 3 11 * + 9 +') == 87
assert postfix_eval('3 4 * 2 5 + / 2 5 4 + * 2 * 36 -') == 0
assert postfix_eval('6') == 6
print("Test Success!")
test_cases()
def __init__(self, capacity_per_stack):
self.capacity_per_stack = capacity_per_stack
self.stack = MyStack(100)
self.stack.push(MyStack(capacity_per_stack))
def __init__(self, capacity):
self.output_stack = MyStack(capacity)
self.help_stack = MyStack(capacity)
self.capacity = capacity
self.current_capacity = capacity
def __init__(self):
self.main_stack = MyStack()
def __init__(self):
super(MinStack, self).__init__()
self.local_mins = MyStack()
