CC4.6.java

    public TreeNode getNext(TreeNode node) {
        if (node.right != null)
            return getMin(node.right);
        TreeNode parent = node.parent;
        while (parent != null && parent.right == node) {
            node = parent;
            parent = node.parent;
        }
        return parent;
    }
    
    private TreeNode getMin(TreeNode node) {
        while (node.left != null)
            node = node.left;
        return node;
    }