Question: WAP to swap alternate nodes in a link list. Play with pointer, don't swap the values.
Algorithm: Only trick to note here is to reserve the third node while swapping two nodes. Rest is pretty simple and doesn't need an explanation.
void swap (struct list **list1)
struct list *cur, *tmp, *next;
cur = *list1;
if(cur && cur->next)
*list1 = cur->next;
//To make sure that we have at least 2 more elements to be swapped.
while(cur && cur->next)
next = cur->next;
tmp = next->next;
next->next = cur;
//We have to make 1->next as 4 in above example (figure).
cur->next = tmp->next;
cur = tmp;
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