Lowest Common Ancestor of a Binary Tree

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 `p` and `q` as the lowest node in `T` 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` and `q` will exist in the tree.