Package g0201_0300.s0236_lowest_common_ancestor_of_a_binary_tree

Class Solution

  • public class Solution
extends Object
    236 - Lowest Common Ancestor of a Binary Tree\. Medium 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](https://en.wikipedia.org/wiki/Lowest_common_ancestor): “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:** ![](https://assets.leetcode.com/uploads/2018/12/14/binarytree.png) **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:** ![](https://assets.leetcode.com/uploads/2018/12/14/binarytree.png) **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.