Balanced Parentheses

Question

QUESTION :
Parentheses are balanced, if all opening parentheses have their corresponding closing parentheses.

Given an expression as input, we need to find out whether the parentheses are balanced or not.
For example, "(x+y)*(z-2*(6))" is balanced, while "7-(3(2*9))4) (1" is not balanced.

MY TRY (USING STACK) :
def areBracketsBalanced(expr):
stack = []

for char in expr:
if char in ["("]:
stack.append(char)

else:
if char in ['1', '2', '3', '4', '5', '6', '7', '8', '9', 'x', 'y', 'z', '+', '*', '-']:
pass
if not stack:
return False
current_char = stack.pop()
if current_char == '(':
if char != ")":
return False

if stack:
return False
return True

if __name__ == "__main__":
expr = input()

if areBracketsBalanced(expr):
print("True")
else:
print("False")

WITHOUT STACK :
def balanced(expression):
openb = 0
closeb = 0
for i in expression:
if i == '(':
openb += 1
elif i == ')':
closeb += 1

if openb == closeb:
return True
else:
return False

print(balanced(input()))

i'm unable to get solve all the test cases

Answer 1

One problem might be a simple )(.

Without stack:
Use only one counter and add 1 for "( and substract 1 for ")".
Additionally check that counter never becomes less than 0.

With stack
append "(" if found.
Pop "(" if ")" found. Wrap it into try/catch

In both cases finally counter and stack must be zero/empty.

Answer 2

Oma Falk
Thank you 😊

Answer 3

x =" (1+2)*3+(7*(6+5))*4"

def bal(s):
opn = s.count("(")
cls = s.count(")")
if opn == cls:
return True
else:
return False
print(bal(x))