Top MCQs on Linked List Data Structure with Answers

Question 1

What does the following function do for a given Linked List with first node as head?

void fun1(struct node* head)
{
  if(head == NULL)
    return;
  
  fun1(head->next);
  printf("%d  ", head->data);
}

• Prints all nodes of linked lists

• Prints all nodes of linked list in reverse order

• Prints alternate nodes of Linked List

• Prints alternate nodes in reverse order

Question 2

Which of the following points is/are true about Linked List data structure when it is compared with array?

• Arrays have better cache locality that can make them better in terms of performance.

• It is easy to insert and delete elements in Linked List

• Random access is not allowed in a typical implementation of Linked Lists

• The size of array has to be pre-decided, linked lists can change their size any time.

• All of the above

Question 3

Consider the following function that takes reference to head of a Doubly Linked List as parameter. Assume that a node of doubly linked list has previous pointer as prev and next pointer as next. 

C

void fun(struct node **head_ref)
{
    struct node *temp = NULL;
    struct node *current = *head_ref;

    while (current !=  NULL)
    {
        temp = current->prev;
        current->prev = current->next;
        current->next = temp;
        current = current->prev;
    }

    if(temp != NULL )
        *head_ref = temp->prev;
}

Assume that reference of head of following doubly linked list is passed to above function 1 <--> 2 <--> 3 <--> 4 <--> 5 <-->6. What should be the modified linked list after the function call?

• 2 <--> 1 <--> 4 <--> 3 <--> 6 <-->5

• 5 <--> 4 <--> 3 <--> 2 <--> 1 <-->6.

• 6 <--> 5 <--> 4 <--> 3 <--> 2 <--> 1.

• 6 <--> 5 <--> 4 <--> 3 <--> 1 <--> 2

Question 4

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.

• *head_ref = prev;

• *head_ref = current;

• *head_ref = next;

• *head_ref = NULL;

Question 5

What is the output of following function in which start is pointing to the first node of the following linked list 1->2->3->4->5->6 ?

C

void fun(struct node* start)
{
  if(start == NULL)
    return;
  printf(\"%d  \", start->data); 
 
  if(start->next != NULL )
    fun(start->next->next);
  printf(\"%d  \", start->data);
}

• 1 4 6 6 4 1

• 1 3 5 1 3 5

• 1 2 3 5

• 1 3 5 5 3 1

Question 6

The following C function takes a simply-linked list as input argument. It modifies the list by moving the last element to the front of the list and returns the modified list. Some part of the code is left blank. Choose the correct alternative to replace the blank line. 

C

typedef struct node 
{
  int value;
  struct node *next;
}Node;
 
Node *move_to_front(Node *head) 
{
  Node *p, *q;
  if ((head == NULL: || (head->next == NULL)) 
    return head;
  q = NULL; p = head;
  while (p-> next !=NULL) 
  {
    q = p;
    p = p->next;
  }
  _______________________________
  return head;
}

• q = NULL; p->next = head; head = p;

• q->next = NULL; head = p; p->next = head;

• head = p; p->next = q; q->next = NULL;

• q->next = NULL; p->next = head; head = p;

Question 7

The following  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? 

Java

class Node {
    int value;
    Node next;
}

void rearrange(Node list) {
    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 != null ? p.next : null;
    }
}

• 1,2,3,4,5,6,7

• 2,1,4,3,6,5,7

• 1,3,2,5,4,7,6

• 2,3,4,5,6,7,1

Question 8

Suppose each set is represented as a linked list with elements in arbitrary order. Which of the operations among union, intersection, membership, cardinality will be the slowest? (GATE CS 2004)

• union 

•  membership

• cardinality

•  union, intersection

Question 9

Consider the function f defined below. 

c

struct item 
{ 
  int data; 
  struct item * next; 
}; 

int f(struct item *p) 
{ 
  return (
          (p == NULL) || 
          (p->next == NULL) || 
          (( p->data <= p->next->data) && f(p->next))
         ); 
} 

For a given linked list p, the function f returns 1 if and only if (GATE CS 2003)

• not all elements in the list have the same data value.

• the elements in the list are sorted in non-decreasing order of data value

• the elements in the list are sorted in non-increasing order of data value

• None of them

Question 10

A circularly linked list is used to represent a Queue. A single variable p is used to access the Queue. To which node should p point such that both the operations enQueue and deQueue can be performed in constant time? (GATE 2004) 

• rear node

• front node

• not possible with a single pointer

• node next to front