/* program to count the number of node in linked list */
Singly Link list A singly link list's node is divided into twofield. The first field
holds information about the node, and second field holds the reference of next node. When we link all node is some order
then it becomes Singly Link list. In singly link list we have only one reference
of next node, so in singly link list we can travels in only one way.
The reference (link) points to the next node in the list, or to a null value( if its last node).
For Singly Link list we need one Head reference to point to the First node of the list.