Alternating split of a given Singly Linked List | GeeksforGeeks

Alternating split of a given Singly Linked List 

Method 2(Using Dummy Nodes)
Here is an alternative approach which builds the sub-lists in the same order as the source list. The code uses a temporary dummy header nodes for the ‘a’ and ‘b’ lists as they are being built. 

void AlternatingSplit(struct node* source, struct node** aRef,

                            struct node** bRef)

{

  struct node aDummy;

  struct node* aTail = &aDummy; /* points to the last node in 'a' */

  struct node bDummy;

  struct node* bTail = &bDummy; /* points to the last node in 'b' */

  struct node* current = source;

  aDummy.next = NULL;

  bDummy.next = NULL;

  while (current != NULL)

  {

    MoveNode(&(aTail->next), &current); /* add at 'a' tail */

    aTail = aTail->next; /* advance the 'a' tail */

    if (current != NULL)

    {

      MoveNode(&(bTail->next), &current);

      bTail = bTail->next;

    }

  }

  *aRef = aDummy.next;

  *bRef = bDummy.next;

}

void MoveNode(struct node** destRef, struct node** sourceRef)

{

  /* the front source node  */

  struct node* newNode = *sourceRef;

  assert(newNode != NULL);

  /* Advance the source pointer */

  *sourceRef = newNode->next;

  /* Link the old dest off the new node */

  newNode->next = *destRef;

  /* Move dest to point to the new node */

  *destRef = newNode;

}

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