Hullo, heres my problems I need to write a mergesort variant for class that works with LinkedLists instead of arrays. Ive got the code down fine but heres the problem. When i call a "split" method to split the Lists

public void split(LinkedList listA, LinkedList listB){
...
}

public LinkedList mergeSort(LinkedList listA){
   if(listA.size()<1)
        return listA;
   if(listA.size()==0)
        return null;
   LinkedList listB=new LinkedList();
   split(listA, listB);
   //Got an outputting debug line here
   return merge(mergeSort(listA),mergeSort(listB));
}

Don't even bother with the merge method, because its not even going their because the lists arent being split. Its running infnitely with the lists never getting smaller. I know that its because when i change the lists in the split method the mergeSort method doesnt see these changes, but how can I "pass them by reference" to borrow the C++ terminology? I also can't change it to just put the split code inside mergeSort, was given to me as an assignment like this. Thx in adavnace,
Troubled,Confused, and a little hungry

: Hullo, heres my problems I need to write a mergesort variant for class that works with LinkedLists instead of arrays. Ive got the code down fine but heres the problem. When i call a "split" method to split the Lists
:

: public void split(LinkedList listA, LinkedList listB){
: ...
: }
: 

:

: public LinkedList mergeSort(LinkedList listA){
:    if(listA.size()<1)
:         return listA;
:    if(listA.size()==0)
:         return null;
:    LinkedList listB=new LinkedList();
:    split(listA, listB);
:    //Got an outputting debug line here
:    return merge(mergeSort(listA),mergeSort(listB));
: }
: 

: Don't even bother with the merge method, because its not even going their because the lists arent being split. Its running infnitely with the lists never getting smaller. I know that its because when i change the lists in the split method the mergeSort method doesnt see these changes, but how can I "pass them by reference" to borrow the C++ terminology? I also can't change it to just put the split code inside mergeSort, was given to me as an assignment like this. Thx in adavnace,
: Troubled,Confused, and a little hungry
:


Why do you have these two conditionals?

if(listA.size()<1)
return listA;
if(listA.size()==0)
return null;

Assuming your list can't have a negative size(which wouldn't make sense), they do the same thing, return if the list is size 0.

What does the code for split look like? It is tad hard to tell you why the lists aren't being split when you don't post the code. :)

Remember that LL are not like arrays, you have to 'walk' out to the middle of the list.

: : Hullo, heres my problems I need to write a mergesort variant for class that works with LinkedLists instead of arrays. Ive got the code down fine but heres the problem. When i call a "split" method to split the Lists
: :

: : public void split(LinkedList listA, LinkedList listB){
: : ...
: : }
: : 

: :

: : public LinkedList mergeSort(LinkedList listA){
: :    if(listA.size()<1)
: :         return listA;
: :    if(listA.size()==0)
: :         return null;
: :    LinkedList listB=new LinkedList();
: :    split(listA, listB);
: :    //Got an outputting debug line here
: :    return merge(mergeSort(listA),mergeSort(listB));
: : }
: : 

: : Don't even bother with the merge method, because its not even going their because the lists arent being split. Its running infnitely with the lists never getting smaller. I know that its because when i change the lists in the split method the mergeSort method doesnt see these changes, but how can I "pass them by reference" to borrow the C++ terminology? I also can't change it to just put the split code inside mergeSort, was given to me as an assignment like this. Thx in adavnace,
: : Troubled,Confused, and a little hungry
: :
:
:
: Why do you have these two conditionals?
:
: if(listA.size()<1)
: return listA;
: if(listA.size()==0)
: return null;
:
: Assuming your list can't have a negative size(which wouldn't make sense), they do the same thing, return if the list is size 0.
:
: What does the code for split look like? It is tad hard to tell you why the lists aren't being split when you don't post the code. :)
:
: Remember that LL are not like arrays, you have to 'walk' out to the middle of the list.
:


yea ive made sure to walk out in the split code..here it is for further clarification

public void split(LinkedList listA, LinkedList listB)
  { 
    LinkedList tA=new LinkedList();
    LinkedList tB=new LinkedList();
    int first=0, last=listA.size()-1;
    int mid=(first+last)/2;
    for(int i=first;i<=mid;i++)
        tA.addLast(listA.get(i));
    for(int j=mid+1;j<=last;j++)
        tB.addLast(listA.get(j));
    listA=tA;
    listB=tB;
  }

ive tested the split code by itself and it does work properly, that is not the problem.

Oh the <1 was a typo on my part...it is an equals sign in the true code