leetcood学习笔记-20

str1 = "hi hello world"
print(str1.split(" "))
输出：
[‘hi‘, ‘hello‘, ‘world‘]

l = ["hi","hello","world"]
print(" ".join(l))
输出：
hi hello world

class Solution:
    def isValid(self, s: str) -> bool:
        dic = {"(": ")", "{": "}", "[": "]",}
        l = []
        for i in range(len(s)):
            if s[i] in dic:#此处在字典中的是左括号！
                l.append(s[i])
            else:
                if len(l)==0:
                    return False
                elif dic[l.pop()]!=s[i]:
                    return False
        if l==[]:
            return True

        else:
            return False

class Solution:
    def isValid(self, s: str) -> bool:
        dic = {"(": ")", "{": "}", "[": "]",}
        l = []
        for i in s:
            if i in dic:
                l.append(i)
            elif len(l)==0 or dic[l.pop()]!=i:
                    return False     
        return not l

class Solution:
    def isValid(self, s):
        while ‘{}‘ in s or ‘()‘ in s or ‘[]‘ in s:
            s = s.replace(‘{}‘, ‘‘)
            s = s.replace(‘[]‘, ‘‘)
            s = s.replace(‘()‘, ‘‘)
        return s == ‘‘