leetCode练题——20. Valid Parentheses

1、题目

20. Valid Parentheses——Easy 

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:

1. Open brackets must be closed by the same type of brackets.
2. Open brackets must be closed in the correct order.

Note that an empty string is also considered valid.

Example 1:

Input: "()"
Output: true

Example 2:

Input: "()[]{}"
Output: true

Example 3:

Input: "(]"
Output: false

Example 4:

Input: "([)]"
Output: false

Example 5:

Input: "{[]}"
Output: true

题目 大致意思是判断给的三种括号组成的字符串是不是对称的。

2、我的解答(copy大神）

 大神的做法还是采用了特殊符号字典存储，以后这种几个的符号真的可以直接采用字典存储（罗马符号、括号之类的），简单明了。

# -*- coding: utf-8 -*-
# @Time    : 2020/1/31 10:37
# @Author  : SmartCat0929
# @Email   : 1027699719@qq.com
# @Link    : https://github.com/SmartCat0929
# @Site    : 
# @File    : 20. Valid Parentheses(copy大神做法）.py

class Solution:
    def isValid(self, s: str) -> bool:
            bracket_map = {"(": ")", "[": "]", "{": "}"}
            open_par = set(["(", "[", "{"])
            stack = []
            for i in s:
                if i in open_par:
                    stack.append(i)
                elif stack and i == bracket_map[stack[-1]]:
                    stack.pop()
                else:
                    return False
            return stack == []
print(Solution().isValid("{[[(])]}"))