Linked List Interview Questions

A linked list is a type of linear data structure consisting of nodes and a pointer to the node after them. Each node comprises data and a link, or reference, to the next node in the sequence. On the other hand, simple linked lists don't allow random access to data or efficient indexing by themselves. Therefore, it may be necessary to scan most or all of the list elements to perform many fundamental operations, locate a node containing a specific piece of information, or determine where a new node should go.

Learn more facts about Linked list:

• List elements can be easily added or removed without reallocating or reorganizing the entire structure. At the same time, an array must be declared in the source code before compiling and running the program.
• Linked lists can add and remove nodes at any point with a constant number of operations as long as the previous link is kept while the list is being moved through.

We'll cover the most frequently asked Linked List questions and answers for the candidates. Based on

• Freshers
• Experienced 
• FAQs

Top 10 Frequently Asked Linked List Interview Questions

1. What is a Linked List?
2. What is the purpose of a Linked list?
3. How many points are required to create a short linked list?
4. How linked lists store data?
5. How many pointers does a Singly Linked List need to be represented?
6. Which processes are involved in flattening a linked list?
7. What are the few applications of the linked list?
8. How can a Java program traverse a linked list?
9. How to display a singly linked list from first to last?
10. What is a circular linked list?

If you want to enrich your career and become a professional in Java, then enroll in "Core Java Training". This course will help you to achieve excellence in this domain.

Linked List Interview Questions for Freshers

1) What is a Linked List?

Linked Lists are linear data structures, just like arrays. Instead of storing like an array, links between the elements of a linked list are made using pointers. A linear data structure that can store a collection of items is known as a linked list. The linked list can also be used to store various objects of related types. The list's elements or units are each represented by a node. Each node has its data as well as the address of the node after it. It resembles a chain. 

Related Article: Java Tutorial

2) How many types of Linked Lists exist?

Linked Lists come in a variety of types, including:

• Multiply Linked List
• Singly Linked List
• Circular Linked List
• Doubly Linked List

3) How do you represent a node in a linked list?

The simplest way to represent a node in a linked list is by wrapping the data and the connection in a typedef structure. The structure is then labeled as a Node pointer, indicating that it is a link in a chain.

The representation of a node in a linked list follows:

/*ll stands for linked list*/
typedef struct ll
{
    int data;
    struct ll *next;
    Node;
}

4) What is the purpose of a Linked list?

Similar forms of linear data can be stored in arrays, but arrays have the following limitations.

• The maximum number of elements is required in advance due to the fixed nature of the array sizes. Furthermore, the allocated memory is always equal to the higher limit, regardless of consumption.
• When adding a new element to an existing array, the cost is high because some of the existing elements must be taken to make room for the new ones.

5) How many points are required to create a short linked list?

There are typically three kinds of pointers required to construct an essential linked list:

• To get to the first item in a list, a "head" pointer can be used.
• The last node can be found with the help of a "tail" pointer. The critical feature of the final node is that the pointer that follows it goes nowhere (NULL).
• A pointer references the next node element in each node.

6) What do you mean by Singly Linked List?

When each node in a linked list contains a pointer to the next node, the list is said to be singly linked. In this case, one possible route is represented by a list with exactly one link. There is only one way to get from the first node to the last one.

7) What do you mean by Doubly Linked List?

Pointers (links) to the next and previous nodes in the list are both parts of the doubly linked list. There are two possible names for the arrows connecting the nodes: "forward" and "backward," "next," and "prev" (previous). In the doubly linked list, each node has three fields: a link to the next node, an integer value, and a link to the node before.

To implement a doubly-linked list with only one link field per node, a method (known as XOR-linking) is used. However, this method requires an enhanced ability to perform specific operations on addresses, so it may not be accessible for specific high-level languages.

8) How linked lists store data?

A linked list is a series of nodes linked together. A linear data structure that can store a collection of items is known as a linked list. The linked list can also be used to store various objects of related types.

9) Name some application that uses a linked list.

1. Stacks
2. Queues
3. Trees
4. Graphs
5. Binary tree
6. Unrolled linked list
7. Hash table Etc

10) How many pointers does a Singly Linked List need to be represented?

Three-pointers represent a singly linked list:

• A pointer in each node
• A head pointer
• A tail pointer

Linked List Interview Questions for Experienced

1) What are the Disadvantages of Linked List?

• Linked lists need more memory than arrays. A linked list pointer uses extra memory to store the next entry's address.
• Linking takes longer than arrays. A linked list doesn't provide direct entry access like an array by index. To reach mode n, you must traverse all preceding nodes.
• You can't go backward in a single-linked list, but in a double-linked list, you can because each node has a pointer to the nodes that were connected before it. When a back pointer is run, memory is used.
• A linked list's dynamic memory allocation prevents random access.

2) What are the Advantages of a Linked List?

• A linked list can grow and shrink by allocating and deallocating memory at runtime. Therefore, the linked list's initial size isn't needed.
• Since the linked list's size changes at runtime, there is no memory waste and no need to pre-allocate memory.
• Linked lists are used to build stacks and queues.
• Linked lists make adding and removing items easier. After inserting or deleting an element, only the next pointer's address must be updated.

3) How many pointers do you need to make a simple Linked List work?

To create even the most basic linked list, you'll need three different kinds of pointers:

• A list's "head" pointer specifies the position of the record's beginning.
• You can think of this pointer as a "tail" that always points to the very last node. The critical aspect of the final node is that the pointer it produces points nowhere (NULL).
• Every node contains a pointer that navigates to the next node in the tree.

4) Linked List is a representation of which memory allocation method?

"dynamic memory allocation" is used when talking about linked lists.

5) What are the fundamental differences between Linked Lists and Arrays?

Memory allocation and traversal are two primary areas in which Linked Lists and Arrays diverge significantly. When compared to arrays, linked lists require significantly more memory. Compared to arrays, the traversals performed on linked lists require significantly more time to complete.

Related Article: Array Interview Questions

6) What graphical representation will you use for a linked list?

The data structure treats each item in a linked list as a separate entity. The items are kept in multiple places when you create a linked list. The elements of a Linked List are linked to one another via the pointers. Each node in a list contains two pieces of information: the data and a pointer (also called a link) to the next node in the sequence. The last node contains a reference to nothing. The "head" of a linked list is its starting node. It's important to remember that the head does not refer to a unique node but rather to the root. In this case, the head is treated as a null reference since the list contains no elements.

7) Which processes are involved in flattening a linked list?

Try the below steps that are involved in flattening a linked list are:

• If there is no following linked list or the current linked list is empty, return the current linked list (Base Case).
• Recursively merge the current linked list with the following linked list
• The merging of linked lists should start with the currently active linked list.
• After appending the following linked list to the current one, return the list's head node.

8) What are the few applications of the linked list?

Linked Lists are most commonly used for the following purposes:

• We can build stacks, queues, graphs, and more with linked lists.
• Element insertion at the start and end of a Linked List is possible.

Related Article: LinkedIn Interview Questions

9) How is a node added to the start of a singly linked list?

The following procedures must be carried out to move the node to the head of the list:

• Make a brand new node.
• When a new node is inserted, the head pointer is changed to point to the node's next child.
• Redirect the focus to the newly added node by modifying the current heading.

10) Describe the process for removing the first node from the singly linked list.

To remove the first link from a singly linked list:

• Put the present starting point in a different temporary pointer.
• Advance the initialization cursor by one space.
• We now have a better starting point version, so we can eliminate the temporary node we used before.

Most Common Linked List FAQs

1) How can a Java program traverse a linked list?

In Java, there are various methods for traversing a linked list. For example, we can use conventional for, while, or do-while loops to iterate through the linked list until we reach the end of it. To iterate through a linked list in Java, we can also use the Java 1.5 enhanced for loop or iterator. As of JDK 8, we can traverse a linked list using Java.util.stream.Stream.

2) Mention some interfaces implemented by Linked List in Java.

Java Linked Lists support a variety of interfaces, some of which are more prominent are:

• Queue
• Collection
• Serializable
• Deque
• Cloneable
• List
• Iterable

Related Article: Java Interview Questions

3) What is the time complexity of Linked List operations?

• A linked list's head node is its only access point. It would help if you hopped from node to node to reach your target. Access is O (n).
• In a linked list, searching for a value requires traversing all elements. Therefore, O (n).
• When inserting a node into a linked list, the previous node must be re-pointed to the inserted node, and the newly-inserted node must be re-pointed to the next node. As a result, O (1).
• In a linked list, deleted nodes must be redirected to the next node (the node after the deleted node). O (1) is for Delete.

Related Article: JP Morgan Interview Questions

4) Why does the linked list delete and insert operation have the complexity of O(1)?

When inserting a node in the middle of a linked list, the assumption is that you are already at the address where the node must be inserted. Indexing is handled separately from other tasks. It means that while insertion is O(1), traveling to the middle node takes O(2) (n). If you have a reference, adding to a linked list doesn't require a traversal.

5) How to display a singly linked list from first to last?

To show the Singly Linked List from the beginning to the end,

• Use create to make a linked list ().
• You can't change the address stored in the global variable "start," so you have to declare a temporary variable "temp" of the type node.
• To go from start to end, you should put the address of the starting node in the pointer variable called temp.

6) What is a circular linked list?

A unique type of linked list called a circular linked list has connections between its nodes that form a circle. Because the first node and the last node in a circular linked list are connected, the list is organized in a circle. The conclusion does not contain a NULL.

7) How can we use Java's Stack to find the sum of two linked lists?

To obtain the sum of the linked lists, we compute the sum of values kept at nodes in the exact location. To determine the value of the first node in the final linked list, we sum the values at the first node in both linked lists. If the two linked lists do not have the same length, only the elements from the shorter linked list are added, and the values for the remaining nodes are copied from the long list.

8) What is a Binary Search tree?

When arranging data, a binary search tree follows predetermined rules. The left node's value in a Binary search tree must be less than or equal to that of the parent node, while the right node's value must be greater than or equal to that of the parent node. Both the root's left and suitable child trees undergo a recursive application of this rule.

9) What is the program to add a node to the linked List?

10) How can data be inserted at the beginning of a singly linked list?

A new node must be created, inserted into the linked list by assigning the head pointer to the next pointer of the newly created node, and the head pointer must be updated to point to the new node. Put a temporary node first in the list if you need to.

Node *head;
void InsertNodeAtFront(int data)
{
  /* 1. create the new node*/
  Node *temp = new Node;
  temp->data = data;
  /* 2. insert it at the first position*/
  temp->next = head;
  /* 3. update the head to point to this new node*/
  head = temp;
}

Conclusion

If you've begun preparing for your next linked list interview process, this article will help you get ahead by understanding what questions will be asked during the interview time. However, no matter how complex a linked list interview is, if you can recall the interview questions related to the principles of a node and how it functions, as well as how the various pointer references in your list are organized will help to ace the interview.