#include <iostream>
using namespace std;

class node {
private:
   int payload;
   node *prev, *next;
public:
   node(int i){ payload = i; prev = next = NULL; }
   node(int i, node *p, node *n){
      payload = i; prev = p; next = n; }
   int get(){ return payload; }
   void print1();
   void printprev();
   void printnext();
   void printall();
   node *search(int);
};

/*
 * search for, and insert if necessary,
 * a node containing data payload i.
 */
node * node::search(int i)
{
   if (i == payload)              /* found it here */
      return this;
   else if (i < payload) {        /* go left */
      if (prev == NULL) {         /* insert at beginning */
	 prev = new node(i, NULL, this);
	 return prev;
         }
      else if (i > prev->get()) { /* insert */
         node *mine = new node(i, prev, this);
	 prev->next = mine;
	 prev = mine;
         return mine;
      } else { /* search */
         return prev->search(i);
      }
   }
   else if (i > payload) {
      if (next == NULL) {         /* insert at end */
	 next = new node(i, this, NULL);
	 return next;
         }
      if (i < next->get()) {      /* insert */
         node *mine = new node(i, this, next);
	 next->prev = mine;
	 next = mine;
         return mine;
      } else { /* search */
         return next->search(i);
      }
   }
}

/*
 * Print one node's data payload.
 */
void node::print1()
{
   cout << "   " << payload << endl;
}

/*
 * Print all preceding nodes' payloads.
 */
void node::printprev()
{
   if (prev) {
      prev->print1();
      prev->printprev();
   }
}

/*
 * Print all preceding nodes' payloads.
 */
void node::printprev_nonrecursive()
{
   node *tmp = prev;
   while (tmp != NULL) {
      tmp->print1();
      tmp = tmp->prev;
   }
}

/*
 * Print all preceding nodes' payloads.
 */
void node::kill_everything()
{

}

/*
 * Print all succeeding nodes' payloads.
 */
void node::printnext()
{
   if (next) {
      next->print1();
      next->printnext();
   }
}

/*
 * Print all nodes' payloads, starting from
 * wherever we are at.
 */
void node::printall()
{
   cout << "The head is at " << payload << endl;
   cout << "Its fathers before it are:" << endl;
   printprev();
   cout << "and its descendents are:" << endl;
   printnext();
}

/*
 * demonstration data.
 */
int main()
{
   node *mylist = new node(5);
   mylist = mylist->search(3);
   mylist = mylist->search(13);
   mylist = mylist->search(7);
   mylist = mylist->search(4);
   mylist = mylist->search(9);
   mylist = mylist->search(6);
   mylist->printall();
   return 0;
}