20. Valid Parentheses(python3)

最新推荐文章于 2024-01-23 09:13:42 发布

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最新推荐文章于 2024-01-23 09:13:42 发布

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本文链接：https://blog.youkuaiyun.com/luoshasha1216/article/details/89508496

本文介绍了一种使用堆栈数据结构来验证字符串中括号是否正确配对的方法。通过遍历字符串，利用字典映射检查开闭括号类型是否一致，并确保它们按正确的顺序关闭。文章提供了Python代码实现，展示了如何判断括号序列的有效性。

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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:

Open brackets must be closed by the same type of brackets.
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

解答：

class Solution:
def isValid(self, s):
"""
:type s:str
:rtype :bool
"""
stack=[]
dict={')':'(',']':'[','}':'{'}
for i in range(len(s)):
if(s[i] in dict.values() ):
stack.append(s[i])
elif s[i] in dict.keys():
if stack==[] or dict[s[i]]!= stack.pop():
return False
else:
return False
return stack==[]