Question

Write the output of function1 if it is called with a list with the initial values

{2, 4, 5, 6, 8, 9, 12}. (Show the changes in the list.)

struct node

{

   int value;

   struct node *next;

};

void function1(struct node *list)

{

struct node *p, *q;

  int temp;

  if ((list==NULL) || list->next==NULL)

      return;

  p = list;

  q = list->next;

  while(q!=NULL)

  {

     temp = p->value;

     p->value = q->value;

     q->value = temp;

     p = q->next;

     q = p->next;

  }

}

Answer 1

Initial values in list:
{2, 4, 5, 6, 8, 9, 12}

Dry run of the function:
>> structure pointer p and q declared of type node.
>> integer variable temp is declared.
>> if condition is checked i.e (list == NULL || list->next == NULL) which is false.
>> Now, p is assigned by list which points to 2 and q is assigned by list->next which points to 4.
>> (Now Iteration of while loop starts)

Iter<..1..> temp = p->value i.e temp = 2,
p-> value = q->value i.e p->value = 4,
q->value = temp i.e q->value = 2
p = q->next i.e now p points to node with value 5
q = p->next i.e now q points to node with value 6
current list = {4,2,5,6,8,9,12}

Iter<..2..> temp = p->value i.e temp = 5,
p-> value = q->value i.e p->value = 6,
q->value = temp i.e q->value = 5
p = q->next i.e now p points to node with value 8
q = p->next i.e now q points to node with value 9
current list = {4,2,6,5,8,9,12}

Iter<..3..> temp = p->value i.e temp = 8,
p-> value = q->value i.e p->value = 9,
q->value = temp i.e q->value = 8
p = q->next i.e now p points to node with value 12
q = p->next i.e now q points to node with value NULL
current list = {4,2,6,5,9,8,12}

Now, since q is NULL, execution of while terminates.
(ITERATION STOPS)

Final value of list is:
{4,2,6,5,9,8,12}

Therefore, this function swaps the adjacent node's value.

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