有效的括号

def solve():
    def isValid(s):
        stack = []
        mapping = {')': '(', '}': '{', ']': '['}
        for char in s:
            if char in mapping:
                top = stack.pop() if stack else '#'
                if mapping[char] != top:
                    return False
            else:
                stack.append(char)
        return not stack
    print(isValid('()[]{}'))