Exercise: Questions on Linked List

Questions on Linked List : 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  Correct Prints alternate nodes of Linked List Prints alternate nodes in reverse order
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Questions on Linked List : 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  Correct
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Questions on Linked List : 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.

```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.  Correct 6 <--> 5 <--> 4 <--> 3 <--> 1 <--> 2
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Questions on Linked List : Question 4 :

Which of the following sorting algorithms can be used to sort a random linked list with minimum time complexity?

 Insertion Sort Quick Sort Heap Sort Merge Sort  Correct
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Questions on 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.

```/* 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;  Correct *head_ref = current; *head_ref = next; *head_ref = NULL;
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Questions on Linked List : Question 6 :

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

```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  Correct
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Questions on Linked List : Question 7 :

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.

```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;  Correct
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Questions on Linked List : Question 8 :

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?

```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;
}
}
```

 1,2,3,4,5,6,7 2,1,4,3,6,5,7  Correct 1,3,2,5,4,7,6 2,3,4,5,6,7,1
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Questions on Linked List : Question 9 :

In the worst case, the number of comparisons needed to search a singly linked list of length n for a given element is (GATE CS 2002)

 log 2 n n/2 log 2 n – 1 n  Correct
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Questions on Linked List : Question 10 :

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 only intersection, membership membership, cardinality union, intersection  Correct
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