- 학부유학생 작성
Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.
According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes
q as the lowest node in
T that has both
q as descendants (where we allow a node to be a descendant of itself).”
Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1 Output: 3 Explanation: The LCA of nodes 5 and 1 is 3.
Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 4 Output: 5 Explanation: The LCA of nodes 5 and 4 is 5, since a node can be a descendant of itself according to the LCA definition.
Input: root = [1,2], p = 1, q = 2 Output: 1
- The number of nodes in the tree is in the range
-109 <= Node.val <= 109
p != q
qwill exist in the tree.
Memory Usage: 26.4 MB, less than 17.99% of Python3 online submissions for Lowest Common Ancestor of a Binary Tree.
class Solution: def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode': if not root: return None if root == p or root==q: return root left = self.lowestCommonAncestor(root.left, p, q) right = self.lowestCommonAncestor(root.right, p, q) if left and right: return root return left or right