GATE | GATE CS 2008 | Question 62

The following C function takes a single-linked list of integers as a parameter and rearranges the elements of the list. The function is called with the list containing the integers 1, 2, 3, 4, 5, 6, 7 in the given order. What will be the contents of the list after the function completes execution?

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struct node
{
  int value;
  struct node *next;
};
void rearrange(struct node *list)
{
  struct node *p, * q;
  int temp;
  if ((!list) || !list->next)
      return;
  p = list;
  q = list->next;
  while(q)
  {
     temp = p->value;
     p->value = q->value;
     q->value = temp;
     p = q->next;
     q = p?p->next:0;
  }
}

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(A) 1,2,3,4,5,6,7
(B) 2,1,4,3,6,5,7
(C) 1,3,2,5,4,7,6
(D) 2,3,4,5,6,7,1


Answer: (B)

Explanation:

Given linked list is 1->2->3->4->5->6->7

If you carefully observe the given function,



It just swaps the adjacent values for every pair till it reaches the end.

The modified linked list is 2->1->4->3->6->5->7

See Question 4 of https://www.geeksforgeeks.org/data-structures-and-algorithms-set-15/

This solution is contributed by Anil Saikrishna Devarasetty

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