39 lines
1.2 KiB
Python
39 lines
1.2 KiB
Python
# Definition for a binary tree node.
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# class TreeNode:
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution:
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def leftSearch(self,stack:List[TreeNode],now:Optional[TreeNode]):
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if now==None:
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stack.append(None)
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else:
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stack.append(now.val)
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self.leftSearch(stack,now.left)
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self.leftSearch(stack,now.right)
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def rightSearch(self,stack:List[TreeNode],now:Optional[TreeNode]) -> bool:
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if len(stack)<1:
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return False
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if now==None:
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if not(stack.pop()==now):
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return False
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return True
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elif not self.rightSearch(stack,now.left):
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return False
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elif not self.rightSearch(stack,now.right):
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return False
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elif not stack.pop()==now.val:
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return False
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return True
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def isSymmetric(self, root: Optional[TreeNode]) -> bool:
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stack=[]
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self.leftSearch(stack,root.left)
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isSym=self.rightSearch(stack,root.right)
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if isSym and len(stack)==0:
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return True
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else:
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return False
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