Ansi-C struct og pointer problemer.

Jeg sidder og roder lidt med pointere i Ansi-C, derfor har jeg dette program som bliver ved med at "crashe" pga mine pointere der er udkommenteret i min swap funktion. Kan du hjælpe mig ? hvad gør jeg galt ?

Min kode:

#include <stdlib.h>
#include <stdio.h>
#include <conio.h>

#define STR_AF_LISTE    4

struct node
  {
  int data;
  struct node *pointer_left;
  struct node *pointer_right;
  };

void show( struct node *pointer);
void swap_( struct node *pointer1, struct node *pointer2);

void main()
  {
  int i, j;
  int inputarray[STR_AF_LISTE] = {45, 32, 2, 36};
  struct node datanode[STR_AF_LISTE];

  struct node *pointer_firstnode = NULL;
  struct node *pointer_lastnode = NULL;
  struct node *pointer_temp = NULL;

  /* pointer brugt til show funktion */
  struct node *pointer_show = NULL;

  /* pointer brugt til swap funktion */
  struct node *p1 = NULL;
  struct node *p2 = NULL;

  /* initialiser liste */
  for ( i=0; i<STR_AF_LISTE; i++)
    {
    if ( i == 0 )
      {
      datanode[i].pointer_left  = NULL;
      datanode[i].data          = inputarray[i];
      datanode[i].pointer_right = &datanode[i+1];
      }
    else
      {
      if (i == (STR_AF_LISTE -1))
        {
        datanode[i].pointer_right = NULL;
        }
      else
        {
        datanode[i].pointer_right = &datanode[i+1];
        }
      datanode[i].pointer_left  = &datanode[i-1];
      datanode[i].data          = inputarray[i];
      }
    }

  /* udskriv liste */
  for (i=0; i<STR_AF_LISTE; i++)
    {
    printf("\n[%i] data = %i", i, datanode[i].data);
    printf(" adr [%i] =  %i ", i, &datanode[i]);
    printf("  [%i] left = %i", i, datanode[i].pointer_left);
    printf("  [%i] right = %i", i, datanode[i].pointer_right);
    }

  /* sæt pointere til at pege på første og sidste */
  pointer_firstnode = &datanode[i];
  for (i=0; i<STR_AF_LISTE; i++)
    {
    pointer_lastnode = &datanode[i];
    }

  printf("\n\n\nTilgang vha first og last pointer:\n");
  printf("\nFirst data = %d", pointer_firstnode->data);
  printf("\nLast data  = %d", pointer_lastnode->data);


  pointer_temp = &datanode[i];
  printf("\npointer temp data = %i  >  ", pointer_temp->data);
  pointer_temp = pointer_temp->pointer_right;

  pointer_show = &datanode[3];
  printf("\nShow pointer -> %d", pointer_show->data);
  show(pointer_show);

  p1 = &datanode[1];
  p2 = &datanode[2];

  swap_(p1, p2);

  for (i=0; i<STR_AF_LISTE; i++)
    {
    printf("\n[%i] data = %i", i, datanode[i].data);
    printf(" adr [%i] =  %i ", i, &datanode[i]);
    printf("  [%i] left = %i", i, datanode[i].pointer_left);
    printf("  [%i] right = %i", i, datanode[i].pointer_right);
    }
  getch();
  }


void show( struct node *pointer)
  {
  printf("\nShow function -> %d", pointer->pointer_right);

  while (pointer->pointer_right != NULL)
    {
    printf("\nData = %d  right = %d  left = %d", pointer->data, pointer->pointer_right, pointer->pointer_left);
    pointer++;
    }
  }


void swap_( struct node *pointer1, struct node *pointer2)
  {
  struct node *ptemp = NULL;

  printf("\nSwap p1 = %d", pointer1->data);
  printf("  left = %d", pointer1->pointer_left);
  printf("  right = %d", pointer1->pointer_right);

  printf("\nSwap p2 = %d", pointer2->data);
  printf("  left = %d", pointer2->pointer_left);
  printf("  right = %d", pointer2->pointer_right);

  /* compileren crasher hvis jeg bruger nedestående */
  /*
  ptemp->pointer_left = pointer1->pointer_left;
  ptemp->pointer_right = pointer1->pointer_right;

  pointer1->pointer_left = pointer2->pointer_left;
  pointer1->pointer_right = pointer2->pointer_right;

  pointer2->pointer_left = ptemp->pointer_left;
  pointer2->pointer_right = ptemp->pointer_right;
  */

  printf("\n\nSwap udført");
  printf("\nSwap p1 = %d", pointer1->data);
  printf("  left = %d", pointer1->pointer_left);
  printf("  right = %d", pointer1->pointer_right);

  printf("\nSwap p2 = %d", pointer2->data);
  printf("  left = %d", pointer2->pointer_left);
  printf("  right = %d", pointer2->pointer_right);
  }