{leetcode}/problems/lowest-common-ancestor-of-a-binary-tree-ii/description/[1644. Lowest Common Ancestor of a Binary Tree II - LeetCode^]
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