20.有效的括号.py

#
# @lc app=leetcode.cn id=20 lang=python
#
# [20] 有效的括号
#

# @lc code=start
class Solution(object):
    def isValid(self, s):
        """
        :type s: str
        :rtype: bool
        """
        dic = {'{':'}', '[':']', '(':')', '?':'?'}
        stack = ['?']
        for c in s:
            if c in dic:
                stack.append(c)
            elif dic[stack.pop()] != c:
                return False
        return len(stack) == 1

# @lc code=end