[Leetcode][Python]20: Valid Parentheses

# -*- coding: utf8 -*-‘‘‘__author__ = ‘[email protected]‘

20: Valid Parentheseshttps://oj.leetcode.com/problems/valid-parentheses/

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.

===Comments by Dabay===用一个stack来保存左括号，如果来的是对应的右括号，就pop一个；如果来的是不对应的右括号，直接return False。‘‘‘

class Solution:    # @return a boolean    def isValid(self, s):        stack = []        for c in s:            if c in "([{":                stack.append(c)            else:                if len(stack) == 0:                    return False                if (                    (c == ")" and stack[-1] == "(") or                    (c == "]" and stack[-1] == "[") or                    (c == "}" and stack[-1] == "{")                ):                    stack.pop()                else:                    return False        else:            return len(stack) == 0

def main():    sol = Solution()    print sol.isValid("()[]{}")

if __name__ == ‘__main__‘:    import time    start = time.clock()    main()    print "%s sec" % (time.clock() - start)