题解 | #有效括号序列#

#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param s string字符串 
# @return bool布尔型
#
class Solution:
    def isValid(self , s: str) -> bool:
        # write code here
        list_stack = []
        for letter in s:
            if letter in ['{','[','(']:
                list_stack.append(letter)
            else:
                if list_stack == []:
                    return False
                else:
                    if list_stack[len(list_stack)-1] == '(' and letter != ')':
                        return False
                    elif list_stack[len(list_stack)-1] == '{' and letter != '}':
                        return False
                    elif list_stack[len(list_stack)-1] == '[' and letter != ']':
                        return False
                    else:
                        list_stack.pop(len(list_stack)-1)
        if list_stack != []:
            return False
        else:
            return True