// Chapter 4, p 179
// Displays a circular Linked List
#include <iostream.h>

typedef char dataType;
typedef struct node* ptrType;  //ptr to node

struct node
{  dataType Data;
   ptrType  Next;
}; // end struct

void Display(dataType Data);

void DisplayList(ptrType List)
// ---------------------------------------------------------
// Displays the data in a circular linked list.
// Precondition: List is a pointer variable that points to
// the last node of a circular linked list.
// Postcondition: The data in the linked list is displayed.
// Both the external pointer List and the linked list are unchanged.
// Calls: Display.
// ---------------------------------------------------------
{
   if (List != NULL)
   {  // list is not empty
      ptrType Cur = List;  // start at head of list

   // Loop invariant: Cur points to the next node to display
      do
      {  Cur = Cur->Next;     // point to next node
	 Display(Cur->Data);  // write data portion
      } while (Cur != List);  // quit at end of list
   }  // end if
} // end DisplayList

void Display(dataType Data)
{
   cout << Data << endl;
}  // end Display

// ******* SAMPLE MAIN *********
main()
{
   ptrType LLHead, FirstPtr, TempPtr;

   FirstPtr = new(node); // save ptr to first node
   FirstPtr->Data = 'b';
   TempPtr = FirstPtr;
   TempPtr->Next = new(node);
   TempPtr = TempPtr->Next;
   TempPtr->Data = 'g';
   TempPtr->Next = new(node);
   TempPtr = TempPtr->Next;
   TempPtr->Data = 'm';
   TempPtr->Next = new(node);
   TempPtr = TempPtr->Next;
   LLHead = TempPtr;          // head ptr points to last node
   TempPtr->Data = 'w';
   TempPtr->Next = FirstPtr;  // last node points to first node
   cout << "The current list is:" << "\n";
   DisplayList(LLHead);

   cout << "\nProgram End.\n";

   return 0;
}