In a linked list print odd nodes first and then even nodes and also sort a linked list

#include<iostream.h>

#include<process.h>

#include<conio.h>

class node

{

public:

      node *next;

      int data;

      node()

      {

            next=NULL;

      }

}*start=NULL;

void display()

{

      if(start==NULL)

      {

            cout<<"empty list";

            return;

      }

      node *ptr=start;

      while(ptr!=NULL)

      {

            cout<<"  "<<ptr->data;

            ptr=ptr->next;

      }

}

void insert(int item)

{

      node *newnode = new node;

      newnode->data=item;

      if(start==NULL)

      {

            start=newnode;

            return;

      }

      node *ptr=start;

      while(ptr->next!=NULL)

            ptr=ptr->next;

      ptr->next=newnode;

}

void del(int item)

{

      if(start->data==item)

      {

            start=start->next;

            return;

      }

      node *pre=NULL,*ptr=start;

      while(ptr!=NULL)

      {

            if(ptr->data==item)

            {

                  pre->next=ptr->next;

                  return;

            }

            pre=ptr;

            ptr=ptr->next;

      }

      cout<<"ITEM NOT IN LIST";

}

void sort()

{

      node *min,*parmin;

      for(node *ptr1=start,*parptr1=NULL;ptr1->next!=NULL;)

      {

            min=ptr1;

            for(node *ptr2=ptr1->next,*save=ptr1;ptr2!=NULL;)

            {

                  if(ptr2->data<min->data)

                  {

                        min=ptr2;

                        parmin=save;

                  }

                  save=ptr2;

                  ptr2=ptr2->next;

            }

            if(min!=ptr1)

            {

                  parmin->next=min->next;

                  min->next=ptr1;

                  if(parptr1==NULL)

                  {

                        start=min;

                        parptr1=min;

                  }

                  else

                  {

                        parptr1->next=min;

                        parptr1=min;

                  }

            }

            else

            {

                  parptr1=ptr1;

                  ptr1=ptr1->next;

            }

      }

}

void main()

{

      clrscr();

      cout<<"1.INSERT\n2.DELETE\n3.DISPLAY\n4.ALL ODD FIRST\n";

      cout<<"5.SORT\n6.REVERSE\n7.ALTERNATE REVERSE\n8.Nth ELEMENT FROM LAST\n9.Exit\n";

      int ch,item;

      while(1)

      {

            cout<<"\nchoice? ";

            cin>>ch;

            switch(ch)

            {

                  case 1:     cout<<"ITEM TO INSERT";

                        cin>>item;

                        insert(item);

                        break;

                  case 2:     cout<<"ITEM TO DELETE";

                        cin>>item;

                        del(item);

                        break;

                  case 3:     display();

                        break;

                  case 4:// sort();

                        evenodd();

                        display();

                        break;

                  case 5: sort();

                        display();

                        break;

                  case 6: //node *ptr=reverse(start);

                        //    ptr->next=NULL;

                        i_reverse();

                        break;

                  case 7: kreverse(4);

                        //altreverse();

                        break;

                  case 8: int n;

                        cout<<" ENTER N ";

                        cin>>n;

                        fromlast(n);

                        break;

                  case 9:     exit(0);

            }

      }

}