Inorder Successor in BST Solutions in Java

// Source : http://www.lintcode.com/en/problem/inorder-successor-in-bst/
//          https://leetcode.com/problems/inorder-successor-in-bst/
// Inspired by : http://www.jiuzhang.com/solutions/inorder-successor-in-bst/
// Author : Lei Cao
// Date   : 2015-10-06



package inorderSuccessorInBST;

public class inorderSuccessorInBST {
    public TreeNode inorderSuccessor(TreeNode root, TreeNode p) {
        TreeNode successor = null;
        if (root == null) {
            return null;
        }
        while (root != null && root.val != p.val) {
            if (root.val > p.val) {
                successor = root;
                root = root.left;
            } else {
                root = root.right;
            }
        }

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

        if (root.right == null) {
            return successor;
        }

        root = root.right;
        while (root.left != null) {
            root = root.left;
        }
        return root;
    }
}