LeetCode No.20 | StriveZs的博客

LeetCode No.20

LeetCode第二十题

题目描述

给定一个只包括 ‘(‘,’)’,’{‘,’}’,’[‘,’]’ 的字符串 s ,判断字符串是否有效。

有效字符串需满足:

左括号必须用相同类型的右括号闭合。
左括号必须以正确的顺序闭合。

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示例 1

输入:s = "()"
输出:true
示例 2

输入:s = "()[]{}"
输出:true
示例 3

输入:s = "(]"
输出:false
示例 4

输入:s = "([)]"
输出:false
示例 5

输入:s = "{[]}"
输出:true
 

提示:

1 <= s.length <= 104
s 仅由括号 '()[]{}' 组成

代码

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class Solution(object):
def isValid(self, s):
"""
:type s: str
:rtype: bool
"""

string = list(s)
stack = []
flag = True
for s in string:
if s == '(' or s == '[' or s == '{':
stack.append(s)
elif s == ')':
if len(stack) == 0:
return False
temp = stack.pop()
if temp != '(':
return False
elif s == ']':
if len(stack) == 0:
return False
temp = stack.pop()
if temp != '[':
return False
elif s == '}':
if len(stack) == 0:
return False
temp = stack.pop()
if temp != '{':
return False
if len(stack) != 0:
return False
return True

if __name__ == '__main__':
s = Solution()
print(s.isValid("{{{{"))
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