program for building and printing the elements of the linked list

program for building and printing the elements of the linked list

# include 
   # include 
   struct node
   {
   int data;
   struct node *link;
   };
   struct node *insert(struct node *p, int n)
   {
   struct node *temp;
   /* if the existing list is empty then insert a new node as the
starting node */
   if(p==NULL)
   {
      p=(struct node *)malloc(sizeof(struct node)); /* creates new node
data value passes
   as parameter */

         if(p==NULL)
         {
      printf("Error\n");
             exit(0);
         }
         p-> data = n;
         p-> link = p; /* makes the pointer pointing to itself because it
is a circular list*/
      }
      else
      {
      temp = p;
   /* traverses the existing list to get the pointer to the last node of
   it */
      while (temp-> link != p)
         temp = temp-> link;
            temp-> link = (struct node *)malloc(sizeof(struct node)); /*
   creates new node using
             data value passes as
               parameter and puts its
             address in the link field
             of last node of the
             existing list*/
           if(temp -> link == NULL)
           {
         printf("Error\n");
              exit(0);
           }
           temp = temp-> link;
           temp-> data = n;
           temp-> link = p;
          }
          return (p);
   }
   void printlist ( struct node *p )
   {
   struct node *temp;
    temp = p;
   printf("The data values in the list are\n");
      if(p!= NULL)
      {
      do
            {
            printf("%d\t",temp->data);
            temp=temp->link;
            } while (temp!= p);
      }
      else
         printf("The list is empty\n");
   }

   void main()
   {
      int n;
      int x;
      struct node *start = NULL ;
      printf("Enter the nodes to be created \n");
      scanf("%d",&n);
      while ( n -- > 0 )
      {
   printf( "Enter the data values to be placed in a node\n");
         scanf("%d",&x);
         start = insert ( start, x );
      }
      printf("The created list is\n");
      printlist ( start );
   }

Explanation This program uses a strategy of inserting a node in an existing list to get the list created. An insert function is used for this. The insert function takes a pointer to an existing list as the first parameter, and a data value with which the new node is to be created as a second parameter, creates a new node by using the data value, appends it to the end of the list, and returns a pointer to the first node of the list. Initially the list is empty, so the pointer to the starting node is NULL. Therefore, when insert is called first time, the new node created by the insert becomes the start node. Subsequently, the insert traverses the list to get the pointer to the last node of the existing list, and puts the address of the newly created node in the link field of the last node, thereby appending the new node to the existing list. The main function reads the value of the number of nodes in the list. Calls iterate that many times by going in a while loop to create the links with the specified number of nodes. Points to Remember Linked lists are used when the quantity of data is not known prior to execution. In linked lists, data is stored in the form of nodes and at runtime, memory is allocated for creating nodes. Due to overhead in memory allocation and deallocation, the speed of the program is lower. The data is accessed using the starting pointer of the list.