This is a C++ linked list Question. I need to insert a college class into a link

Question

This is a C++ linked list Question. I need to insert a college class into a linked list in alphabetical order based on the name of the class. I have a problem with my add function. When I add three classes and try to display the classes, the output goes into an infinite loop. Also when you add a class that would go on the end of the list the add function goes into an infinite loop. I think my problem is with the section that adds the node to the end of the linked list. The get_course_number() function returns the string name of the course to be placed in alphabetical order.

Here is my node class:

#ifndef NODE_H
#define NODE_H
#include "course.h"
class node{
public:
   typedef course value_type;
   // Universal constructor
node(value_type d = value_type(), node *l = NULL)
       {data_field = d; link_field = l;}
// Mutator functions
   void set_data(value_type d)
       {data_field = d;}
   void set_link(node *l)
       {link_field = l;}
// Accessor functions
value_type data() const
   {return data_field;}
  
   node* link()
   {return link_field;}
  
   const node* link() const
   {return link_field;}
private:
   value_type data_field;
   node* link_field;
};
#endif

Here is my College Class:

#include "college.h"
#include
#include
#include
#include
using namespace std;

College::College(string x){
   student_name = x;
   head_ptr = NULL;
   curr_ptr = NULL;
   prev_ptr = NULL;
   next_ptr = NULL;
}

College::~College(){
   node * prev_ptr;
   node * curr_ptr;
  
   prev_ptr = curr_ptr = head_ptr;
  
   while (curr_ptr != NULL){
       curr_ptr = prev_ptr->link();
       delete prev_ptr;
       prev_ptr = curr_ptr;
}
   prev_ptr = curr_ptr = head_ptr = NULL;
}

void College::add(course c){
   cout<<"starting add function" << endl;
   prev_ptr = head_ptr;
   next_ptr = head_ptr;
node * temp_ptr = new node(c);
  
   curr_ptr = head_ptr;
  
   if (curr_ptr == NULL) // empty list
   {
       head_ptr = temp_ptr;
   }
   else
   {
       while (curr_ptr != NULL){
           if (curr_ptr->link() == NULL) // end of list
{
               curr_ptr->set_link(temp_ptr);
               break;
           }
           else if ( temp_ptr->data().get_course_number() < curr_ptr->data().get_course_number() )
           // insert temp
           {
               temp_ptr->set_link( curr_ptr->link() );
               curr_ptr->set_link( temp_ptr );
               break;
           }
           curr_ptr->set_link( curr_ptr->link() );
       }
   }
}

void College::display(ostream& cout){
   curr_ptr = head_ptr;
   while(curr_ptr != NULL){

       cout << "Class Number: " << curr_ptr->data().get_course_number() << endl;
       cout << "Class Grade: " << curr_ptr->data().get_number_grade() << endl;
       cout << "Class Hours: " << curr_ptr->data().get_hours() << endl;
      
       curr_ptr = curr_ptr->link();
   }
}

Explanation / Answer

#include "college.h"
#include
#include
#include
#include
using namespace std;

College::College(string x){
   student_name = x;
   head_ptr = NULL;
   curr_ptr = NULL;
   prev_ptr = NULL;
   next_ptr = NULL;
}

College::~College(){
   node * prev_ptr;
   node * curr_ptr;
  
   prev_ptr = curr_ptr = head_ptr;
  
   while (curr_ptr != NULL){
       curr_ptr = prev_ptr->link();
       delete prev_ptr;
       prev_ptr = curr_ptr;
}
   prev_ptr = curr_ptr = head_ptr = NULL;
}

void College::add(course c){
   cout<<"starting add function" << endl;
   prev_ptr = head_ptr;
   next_ptr = head_ptr;
node * temp_ptr = new node(c);
  
   curr_ptr = head_ptr;
  
   if (curr_ptr == NULL) // empty list
   {
       head_ptr = temp_ptr;
   }
   else
   {
       while (curr_ptr != NULL){
           if (curr_ptr->link() == NULL) // end of list
{
               curr_ptr->set_link(temp_ptr);
               break;
           }
           else if ( temp_ptr->data().get_course_number() < curr_ptr->data().get_course_number() )
           // insert temp
           {
               temp_ptr->set_link( curr_ptr->link() );
               curr_ptr->set_link( temp_ptr );
               break;
           }
           curr_ptr->set_link( curr_ptr->link() );
       }
   }
}

void College::display(ostream& cout){
   curr_ptr = head_ptr;
   while(curr_ptr != NULL){

       cout << "Class Number: " << curr_ptr->data().get_course_number() << endl;
       cout << "Class Grade: " << curr_ptr->data().get_number_grade() << endl;
       cout << "Class Hours: " << curr_ptr->data().get_hours() << endl;
      
       curr_ptr = curr_ptr->link();
   }
}

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