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Commit 571defa

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更新 0020.有效的括号.md python部分额外方法提供
补充了题主的方法,改写了原先冗余的做法,可读性提升,PEP8标准
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‎problems/0020.有效的括号.md‎

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Original file line numberDiff line numberDiff line change
@@ -162,18 +162,44 @@ class Solution {
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Python:
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```python3
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# 方法一,仅使用栈,更省空间
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class Solution:
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def isValid(self, s: str) -> bool:
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stack = [] # 保存还未匹配的左括号
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mapping = {")": "(", "]": "[", "}": "{"}
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for i in s:
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if i in "([{": # 当前是左括号,则入栈
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stack.append(i)
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elif stack and stack[-1] == mapping[i]: # 当前是配对的右括号则出栈
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stack = []
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for item in s:
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if item == '(':
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stack.append(')')
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elif item == '[':
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stack.append(']')
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elif item == '{':
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stack.append('}')
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elif not stack or stack[-1] != item:
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return False
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else:
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stack.pop()
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else: # 不是匹配的右括号或者没有左括号与之匹配,则返回false
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return True if not stack else False
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```
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```python3
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# 方法二,使用字典
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class Solution:
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def isValid(self, s: str) -> bool:
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stack = []
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mapping = {
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'(': ')',
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'[': ']',
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'{': '}'
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}
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for item in s:
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if item in mapping.keys():
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stack.append(mapping[item])
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elif not stack or stack[-1] != item:
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return False
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return stack == [] # 最后必须正好把左括号匹配完
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else:
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stack.pop()
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return True if not stack else False
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```
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