def balanced_parentheses(paren_str):
"""problem involving applications of stack"""
# filter out all values besides brackets
matches = re.finditer(r'[(){}[\]]+', paren_str)
parsed_iter = itertools.chain.from_iterable(
result.group()
for result in matches)
opening = Stack()
for i in parsed_iter:
if i in ("(", "{", "["):
opening.add(i)
else:
if not opening.isEmpty():
if i == ")" and opening.peek() == "(":
opening.get()
elif i == "}" and opening.peek() == "{":
opening.get()
elif i == "]" and opening.peek() == "[":
opening.get()
else:
return False
else:
return False
return True
def revstringstack(str):
# with stack implemented
stack = Stack()
for char in str:
stack.add(char)
new_str = ''
while not stack.isEmpty():
new_str += stack.get()
return new_str
