31 lines
980 B
Python
31 lines
980 B
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 diameterOfBinaryTree(self, root: Optional[TreeNode]) -> int:
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diameter = 0
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def longest_path(node):
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# nonlocal to access the diameter when doing recursion
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nonlocal diameter
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# if no child
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if not node:
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return 0
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# calculate the longest path for left and right
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left_longest = longest_path(node.left)
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right_longest = longest_path(node.right)
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# check if its bigger than diameter
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diameter = max(diameter, left_longest + right_longest)
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# add the edge to parent while returning
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return max(left_longest, right_longest) + 1
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# do post-tree traversal
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longest_path(root)
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return diameter
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