Java LeetCode 236. The nearest common ancestor of a binary tree

Given a binary tree, find the nearest common ancestor of two specified nodes in the tree.
The definition of the nearest common ancestor in Baidu Encyclopedia is: "For two nodes p and q of the rooted tree T, the nearest common ancestor is expressed as a node x, so that x is the ancestor of p and q and the depth of x is as large as possible (A node can also be its own ancestor)."
For example, given the following binary tree: root = [3,5,1,6,2,0,8,null,null,7,4]

If there is no left (right) subtree, return to the first right (left) subtree found,

If the left and right subtrees are found, the root node is returned directly

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    
    
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
    
    
        if(root==null||root==p||root==q){
    
    
            return root;
        }

        TreeNode ps =lowestCommonAncestor(root.left,p,q);
        TreeNode qs =lowestCommonAncestor(root.right,p,q);

        if(ps==null){
    
    
            return qs;
        }
        if(qs==null){
    
    
            return ps;
        }
        return root;
    }
}