Leetcode20-Valid Parentheses(Python3)

20. 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.

My Solution

class Solution(object):
    def isValid(self, s):
        """
        :type s: str
        :rtype: bool
        """
        i, time, len_s = 0, 0, len(s)
        while time < len_s:
            if s[i: i+2] == '()' or s[i: i+2] == '[]' or s[i: i+2] == '{}':
                s = s[:i] + s[i+2:]
                if i != 0:
                    i = 1
                else:
                    time += 1
            else:
                i += 1
            time += 1
        if len(s) == 0:
            return True
        else:
            return False

Reference (转)

class Solution:
    # @return a boolean
    def isValid(self, s):
        stack = []
        dict = {"]":"[", "}":"{", ")":"("}
        for char in s:
            if char in dict.values():
                stack.append(char)
            elif char in dict.keys():
                if stack == [] or dict[char] != stack.pop():
                    return False
            else:
                return False
        return stack == []