In [11]:

    

# https://www.codewars.com/kata/52774a314c2333f0a7000688/train/python

def valid_parentheses(string):
    paren_stack = []
    if string.isspace(): return False
    
    for i in string:
        if i == "(":
            paren_stack.append(i)
        elif i == ")":
            if len(paren_stack) > 0 and paren_stack[-1] == "(":
                paren_stack.pop()
                continue
            else:
                return False
        else: # any other char
          pass
          
    if len(paren_stack) == 0:
        return True
        
    return False


    

In [13]:

    

print valid_parentheses("  (") # False
print valid_parentheses(")test") # False
print valid_parentheses("") # True
print valid_parentheses("hi())(") # False
print valid_parentheses("hi(hi)()") # True


    

    




False
False
True
False
True

In [8]:

    

# clever solution :)
def valid_parentheses_codeWars(string):
    cnt = 0
    for char in string:
        if char == '(': cnt += 1
        if char == ')': cnt -= 1
        if cnt < 0: return False
    return True if cnt == 0 else False


    

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