public static void main(String args[]){
        BinaryTree bt = new BinaryTree();
        Node head = null;
        head = bt.addNode(3, head);
        head = bt.addNode(-6, head);
        head = bt.addNode(-7, head);
        head = bt.addNode(2, head);
        head = bt.addNode(9, head);
        head = bt.addNode(6, head);
        head = bt.addNode(11, head);
        head = bt.addNode(13, head);
        head = bt.addNode(12, head);
        VerticalTreePrinting vtp = new VerticalTreePrinting();
        vtp.printVertical(head);
    }
http://www.geeksforgeeks.org/print-binary-tree-vertical-order-set-2/
src/com/interview/tree/VerticalTreePrinting.java