栈和队列_leetcode20

#coding=utf-8
# 解题思路：栈   20190302 找工作期间

class Solution(object):
    def isValid(self, s):
        """
        :type s: str
        :rtype: bool
        """
        stack = []

        for i in s :
            if i == "(" or i == "{" or i == "[":
                stack.append(i)
            else:

                if len(stack) == 0:
                    return False

                else:
                    match = None
                    topItem = stack.pop()

                    if i == ')':
                        match = '('

                    if i == ']':
                        match = '['

                    if i == '}':
                        match = '{'


                    if topItem != match:
                        return False

        if len(stack) > 0:
            return False
        else:
            return True


s = Solution()

print s.isValid("()")