1650. Lowest Common Ancestor of a Binary Tree III
https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree-iii
Description
Given two nodes of a binary tree p
and q
, return their lowest common ancestor (LCA).
Each node will have a reference to its parent node. The definition for Node
is below:
class Node {
public int val;
public Node left;
public Node right;
public Node parent;
}
According to the definition of LCA on Wikipedia: "The lowest common ancestor of two nodes p and q in a tree T is the lowest node that has both p and q as descendants (where we allow a node to be a descendant of itself)."
Example 1:

**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.
Example 2:

**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.
Example 3:
**Input:** root = [1,2], p = 1, q = 2
**Output:** 1
Constraints:
The number of nodes in the tree is in the range
[2, 105]
.-109 <= Node.val <= 109
All
Node.val
are unique.p != q
p
andq
exist in the tree.
ac
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