public static void main(String args[]){
        NodesAtDistanceK nad = new NodesAtDistanceK();
        Node root = null;
        BinaryTree bt = new BinaryTree();
        root = bt.addNode(10, root);
        root = bt.addNode(3, root);
        root = bt.addNode(-1, root);
        root = bt.addNode(8, root);
        root = bt.addNode(-6, root);
        root = bt.addNode(-11, root);
        root = bt.addNode(18, root);
        root = bt.addNode(11, root);
        root = bt.addNode(13, root);
        root = bt.addNode(26, root);
        root = bt.addNode(27, root);
        nad.printNodes(root, 11, 2);
    }
http://www.geeksforgeeks.org/print-nodes-distance-k-given-node-binary-tree/
Test case 
k should not be negative
k could be very big number which means nothing was found
dest might/might not exists in the tree
root could be null
src/com/interview/tree/NodesAtDistanceK.java