main_linked_list.cpp

//to compile, do g++ -c main_linked_list.cpp
//to link, do g++ -o main_linked_list main_linked_list.o

#include <iostream>

using namespace std;

struct residue
 {
   //char *name;
   string name;
   int num;
   residue *next;

 };


struct node
  {  char name[20];    // Name of up to 20 letters
     int age;          // D.O.B. would be better
     float height;     // In metres
     node *nxt;        // Pointer to next node
  };

node *start_ptr = NULL;
node *current;		 // Used to move along the list
int option = 0;

void add_node_at_end()
  {  node *temp, *temp2;   // Temporary pointers

     // Reserve space for new node and fill it with data
     temp = new node;
     cout << "Please enter the name of the person: ";
     cin >> temp->name;
     cout << "Please enter the age of the person : ";
     cin >> temp->age;
     cout << "Please enter the height of the person : ";
     cin >> temp->height;
     temp->nxt = NULL;

     // Set up link to this node
     if (start_ptr == NULL)
       { start_ptr = temp;
	 //current = start_ptr;
       }
     else
       { temp2 = start_ptr;
         // We know this is not NULL - list not empty!
         while (temp2->nxt != NULL)
           {  temp2 = temp2->nxt;
              // Move to next link in chain
           }
         temp2->nxt = temp;
       }
     
       current=temp;
        
  }

void display_list()
  {  node *temp;
     temp = start_ptr;
     cout << endl;
     if (temp == NULL)
       cout << "The list is empty!" << endl;
     else
       { while (temp != NULL)
	   {  // Display details for what temp points to
              cout << "Name : " << temp->name << " ";
              cout << "Age : " << temp->age << " ";
	      cout << "Height : " << temp->height;
	      if (temp == current)
		cout << " <-- Current node";
              cout << endl;
	      temp = temp->nxt;

	   }
	 cout << "End of list!" << endl;
       }
  }

void delete_start_node()
   { node *temp;
     temp = start_ptr;
     start_ptr = start_ptr->nxt;
     delete temp;
   }

void delete_end_node()
   { node *temp1, *temp2;
     if (start_ptr == NULL)
          cout << "The list is empty!" << endl;
     else
        { temp1 = start_ptr;
          if (temp1->nxt == NULL)
             { delete temp1;
               start_ptr = NULL;
             }
          else
             { while (temp1->nxt != NULL)
                { temp2 = temp1;
                  temp1 = temp1->nxt;
                }
               delete temp1;
               temp2->nxt = NULL;
             }
        }
   }

void move_current_on ()
   { if (current->nxt == NULL)
      cout << "You are at the end of the list." << endl;
     else
      current = current->nxt;
   }

void move_current_back ()
   { if (current == start_ptr)
      cout << "You are at the start of the list" << endl;
     else
      { node *previous;     // Declare the pointer
        previous = start_ptr;

        while (previous->nxt != current)
          { previous = previous->nxt;
          }
        current = previous;
      }
   }

int main()
  {  
     residue *temp;
      
     temp=new residue;
     
     cout << "Please enter the name of the residue: ";
     cin>>temp->name;

     start_ptr = NULL;
     do
	{
	  display_list();
	  cout << endl;
	  cout << "Please select an option : " << endl;
	  cout << "0. Exit the program." << endl;
	  cout << "1. Add a node to the end of the list." << endl;
	  cout << "2. Delete the start node from the list." << endl;
	  cout << "3. Delete the end node from the list." << endl;
	  cout << "4. Move the current pointer on one node." << endl;
          cout << "5. Move the current pointer back one node." << endl;
          cout << endl << " >> ";
	  cin >> option;

	  switch (option)
	    {
	      case 1 : add_node_at_end(); break;
	      case 2 : delete_start_node(); break;
	      case 3 : delete_end_node(); break;
	      case 4 : move_current_on(); break;
              case 5 : move_current_back();
	    }
	}
     while (option != 0);
  }