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31 lines
829 B
Python
31 lines
829 B
Python
'''
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Given the root of a binary tree, return the number of uni-value subtrees.
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A uni-value subtree means all nodes of the subtree have the same value.
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'''
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def count_unival(root: Optional[TreeNode]) -> int:
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global count = 0
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def dfs(node):
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if not node:
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return True
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is_uni_left = dfs(node.left)
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is_uni_right = dfs(node.right)
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if is_uni_left and is_uni_right:
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if node.left and node.left.val != node.val:
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return False
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if node.right and node.right.val != node.val:
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return False
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self.count += 1
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return True
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return False
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dfs(root)
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return count
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