Data Structures | Linked List | Question 5

The following function reverse() is supposed to reverse a singly linked list. There is one line missing at the end of the function. 

C

/* Link list node */
struct node
{
    int data;
    struct node* next;
};

/* head_ref is a double pointer which points to head (or start) pointer
  of linked list */
static void reverse(struct node** head_ref)
{
    struct node* prev   = NULL;
    struct node* current = *head_ref;
    struct node* next;
    while (current != NULL)
    {
        next  = current->next;
        current->next = prev;
        prev = current;
        current = next;
    }
    /*ADD A STATEMENT HERE*/
}

What should be added in place of \”/*ADD A STATEMENT HERE*/\”, so that the function correctly reverses a linked list.

(A)

*head_ref = prev;

(B)

*head_ref = current;

(C)

*head_ref = next;

(D)

*head_ref = NULL;

Answer: (A)

Explanation:

The statement to update the head pointer could be as follows

*head_ref = prev;

This statement sets the value of *head_ref (which is a double pointer) to the value of prev, which is the new head of the reversed list.

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