题目：
Given a string containing just the characters ‘(‘, ‘)‘, ‘{‘, ‘}‘, ‘[‘ and ‘]‘, determine if the input string is valid.
The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]" are not.
链接：http://leetcode.com/problems/valid-parentheses/
一刷，右半部分的else中的两次判断可以合在一句，但是容易忽略pop，不够直观。
class Solution(object): def isValid(self, s): """ :type s: str :rtype: bool """ stack = [] parenthese = { ‘(‘: ‘)‘, ‘[‘: ‘]‘, ‘{‘: ‘}‘ } for char in s: if char in parenthese: stack.append(char) else: if not stack: return False prev = stack.pop() if parenthese[prev] != char: return False return False if stack else True
原文：http://www.cnblogs.com/panini/p/5569202.html