题解 | #有效括号序列#

class Solution:
    def isValid(self , s: str) -> bool:
        if len(s) == 0:
            return True
        elif len(s) % 2 == 1:
            return False
        else:
            stack = []
            for c in s:
                if c in ['(','{','[']:
                    stack.append(c)
                elif len(stack) > 0:
                    last = stack.pop()
                    if c == ')' and last != '(':
                        return False
                    elif c == '}' and last != '{':
                        return False
                    elif c == ']' and last != '[':
                        return False
                else: # 栈已空，c却是右半边
                    return False
            else: # 循环正常走完
                if len(stack) == 0:
                    return True
                else: # 栈不空
                    return False