public static void main(String args[]){
        BinaryTree bt = new BinaryTree();
        Node head = null;
        head = bt.addNode(10, head);
        head = bt.addNode(15, head);
        head = bt.addNode(19, head);
        head = bt.addNode(17, head);
        head = bt.addNode(11, head);

        head = bt.addNode(-11, head);


        TreeTraversals tt = new TreeTraversals();
        tt.postOrder(head);
        System.out.println();
        tt.postOrderItr(head);
        System.out.println();
        tt.postOrderItrOneStack(head);
    }
Youtube link - https://youtu.be/nzmtCFNae9k
Youtube link - https://youtu.be/elQcrJrfObg
Youtube link - https://youtu.be/qT65HltK2uE
Youtube link - https://youtu.be/ZM-sV9zQPEs

http://www.geeksforgeeks.org/inorder-tree-traversal-without-recursion/
http://www.geeksforgeeks.org/inorder-tree-traversal-without-recursion-and-without-stack/
http://www.geeksforgeeks.org/iterative-preorder-traversal/
src/com/interview/tree/TreeTraversals.java