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
        stack=[]
        for i in range(len(s)):
            if s[i]=="(" or s[i]=="{" or s[i]=="[":
                stack.append(s[i])
            elif stack and s[i]==")":

                if stack[-1]=="(":
                    stack.pop()
                else:
                    return False
            elif stack and s[i]=="}":

                if stack and stack[-1]=="{":
                    stack.pop()
                else:
                    return False
            elif stack and s[i]=="]":

                if stack[-1]=="[":
                    stack.pop()
                else:
                    return False
            else:
                return False
        if len(stack)==0:
            return True
        else:
            return False