problem with pointers when sorting a double linked list using merge sort

[nabh4u]

hi friends,

i have a program where i have to sort a double linked list using merge sort. i am having problem with changing the pointers of the list, like the previous and the next pointers of a node. i am unable to understand how can i change those. i tried something but that is not working. please help me as soon as possible as i have a deadline. here is a sample :

int merge(low,mid,high)
{
   int i,j,k;
   i=low;
   j=mid+1;
   list *temp,*temp1;
   while(i<=mid && j<=high)
   {
      if(current->n <= current->next->n)
      {
         current=current->next;
         i++;
      }
      else
      {
         temp->prev=current->prev;
         temp->next=current->next;
         current->prev=current->next->prev;
         current->next=current->next->next;
         temp1->prev=temp->prev;
         temp1->next=temp->next;
         j++;
      }
   }

current is the pointer pointing to the current node of the list.

this is a kind of implementation i tried. please tell me how should i change the pointers in the list. plese help me, its urgent.

thanx in advance.

[Ganon11]

Is this the exact code you wre using? The function header needs to declare the types of the parameters (i.e. "int low, int mid, int high" instead of "low, mid, high"). Also, there is a curly bracket missing to close the function.

Next, this line

current->prev=current->next->prev;

is kind of redundant. current->next->prev should bring you back to current, so why not write

current->prev = current;

[nabh4u]

Is this the exact code you wre using? The function header needs to declare the types of the parameters (i.e. "int low, int mid, int high" instead of "low, mid, high"). Also, there is a curly bracket missing to close the function.

Next, this line

current->prev=current->next->prev;

is kind of redundant. current->next->prev should bring you back to current, so why not write

current->prev = current;

well tht was the sample code i was using but now i changed it. now when i print the list it goes into an infinte loop but when i print the list in reverse it doesnt print all the nodes and the sequence is also wrong (prints the earlier reverse version where the list is not sorted).
eg: the list is 4 3 1 2
after sorting it should be 1 2 3 4 (forward print)
but when printing in forward it goes into infinte loop with 4
and for reverse print i get 1 2 3 only but it should be 4 3 2 1.

here's the changed code:

int merge(int low,int mid,int high)
{
   int i,j,k;
   i=low;
   j=mid+1;
   list *temp = new list();
   list *temp1=new list();
   current=first;
   temp=current->next;
   temp1->next=current->next;
   temp1->prev=current->prev;
 
   while(i<=mid && j<=high)
   {
      if(current->n <= temp->n)
      {
         current=current->next;
         temp=current->next;
         temp1->next=current->next;
         temp1->prev=current->prev;
         i++;
      }
      else
      {
         current->next=temp->next;
         current->prev=temp;
         temp->next=current;
         temp->prev=temp1->prev;     
         j++;
      }
   } 
}

what about the remaining part of the list? please tell me if this code successfully sorts the link list or not and what is the problem.
please tell me how exactly i should change the pointers.. this is creating a lot of confusion..please correct my code.
thank you in advance...