Splitting linked list into half C programming

Question

I am having some problem when trying to split a linked list into half. Let's say for example my linked list is 2,3,5,6,7. And the first split linked list should contain 2,3,5 and the second one should be 6,7.

I have not actually came out with the code yet as I still need some helps in the pseud code.

int check = size%2
if even
  int half = size/2
  while(ctrFront < half)
    front.insertNode; ctrFront++; update head pointer;
  while(ctrBack < half)
    back.insertNode; ctrBack++; update head pointer;
if odd
  int half = size/2 round up
  while(ctrFront < half + 1)
    front.insertNode; ctrFront++; update head pointer;
  while(ctrBack < half)
    back.insertNode; ctrBack++; update head pointer;

I not sure if this is the correct way as the logic seems a little bit wrong. Any guides?

Thanks in advance.

My advice: Try to implement your pseudo-code, then if you have a problem you can make a question. — 101010, Oct 31 '15 at 14:05
You *do* realize the integer division in C truncates the result? Your `half` can be done as `size+1>>1` without an `if`. — EOF, Oct 31 '15 at 14:05
@Was So Lost That is the original list after the operation will be empty, won't it? — Vlad from Moscow, Oct 31 '15 at 14:40
@VladfromMoscow It supposed to be emptied but somehow mine doesn't clear. It just keep on adding and resulting in error — , Oct 31 '15 at 15:08

Martin James · Answer 1 · 2015-10-31T14:23:01.790

0

Construct two lists. Pop the source list until its is empty, pushing each item alternately onto the new lists. Reseat the head pointer of the source list with one of the new lists.

There, it's easy:

linkedList *newList1=NULL;
linkedList *newList2=NULL;

while(true){
  node *temp;
  node=listPop(&sourceList);
  if(temp==NULL) break;
  listPush(&newList1,temp);
  temp=listPop(&sourceList);
  if(temp==NULL) break;
  listPush(&newList2,temp);
};

edited Oct 31 '15 at 14:23

answered Oct 31 '15 at 14:13

Martin James

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But I didn't want to store them alternately. Mine was just simply splitting into front and back part – Oct 31 '15 at 14:15

Splitting linked list into half C programming

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