Question

I had heard this question from my friend who attended an interview recently:

Given the head of the linked list, Write a function to swap the head with the next element in the linked list and return the pointer to the new head.

Ex:

i/p: 1->2,3,4,5 (the given head is 1)
o/p: 2->1,3,4,5

Answer 1

Assuming

struct node {
    struct node *next;
};
struct node *head;

then the solution might look something like

struct node *next = head->next;
if(next == NULL) return head; // nothing to swap
head->next = next->next;
next->next = head;
head = next;
return next;