Leetcode #285. Inorder Successor in BST

[yokostan]

Recursive solution:

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