def is_balanced(parens: str):
"""Checks to see if a string of parens are balanced"""
stack = Stack()
try:
for paren in parens:
if stack.is_empty() or (not stack.is_empty() and paren == stack.peek()):
stack.push(paren)
else:
stack.pop()
return stack.is_empty()
except IndexError:
return False
def dfsPrint(self, start):
if start is None:
return
stack = Stack()
stack.push(start)
traversal = ""
while len(stack) > 0:
traversal += str(stack.peek().value) + "->"
node = stack.pop()
if node.left:
stack.push(node.left)
if node.right:
stack.push(node.right)
return traversal
class Stack(object):
def __init__(self):
self.ll = LinkedList()
def isEmpty(self):
return self.ll.isEmpty()
def push(self, data):
self.ll.addNode(Node(data))
def pop(self):
self.ll.delEnd()
def peek(self):
return self.ll.returnEndElement()
def size(self):
return self.ll.size()
s = Stack()
s.push(133)
s.push(24)
s.push(123)
s.push(12124)
s.pop()
print s.peek()
print s.size()