1644. Lowest Common Ancestor of a Binary Tree II
https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree-ii
Description
Given the root
of a binary tree, return the lowest common ancestor (LCA) of two given nodes, p
and q
. If either node p
or q
does not exist in the tree, return null
. All values of the nodes in the tree are unique.
According to the definition of LCA on Wikipedia: "The lowest common ancestor of two nodes p
and q
in a binary 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)". A descendant of a node x
is a node y
that is on the path from node x
to some leaf node.
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. A node can be a descendant of itself according to the definition of LCA.
Example 3:

**Input:** root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 10
**Output:** null
**Explanation:** Node 10 does not exist in the tree, so return null.
Constraints:
The number of nodes in the tree is in the range
[1, 104]
.-109 <= Node.val <= 109
All
Node.val
are unique.p != q
Follow up: Can you find the LCA traversing the tree, without checking nodes existence?
ac
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