Top 40 Linked List Interview Questions and Answers (2026)

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Top Linked List Interview Questions and Answers

Getting ready for a data structures interview demands focus on challenges. Linked List Interview Questions reveal problem-solving depth, pointer logic, memory awareness, and how candidates reason through edge cases.

Mastering linked lists opens roles across product teams, platforms, and systems engineering. Practical exposure builds strong technical expertise, analytical thinking, and clean coding habits. From freshers to senior professionals, this skillset supports real debugging, performance analysis, mentoring juniors, and collaborating with managers on scalable solutions using advanced concepts from experience. Read more…

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Top Linked List Interview Questions and Answers

1) Explain what a Linked List is and how it differs from an array.

A linked list is a linear data structure where elements, called nodes, are connected using pointers or references. Each node contains data and a pointer/reference to the next node in the list. Unlike arrays, linked lists do not store elements in contiguous memory.

Key differences between a linked list and an array:

Feature Linked List Array
Memory Allocation Dynamic Static
Element Access Time O(n) O(1)
Insertion/Deletion Efficient (at any position) Costly (needs shifting)
Memory Overhead Extra space for pointers No extra pointer overhead

In summary, linked lists trade off faster insertions and dynamic sizing for slower random access and additional memory overhead due to pointers.

2) What are the different types of Linked Lists?

There are several types of linked lists, and interviewers often ask you to distinguish among them:

  • Singly Linked List: Each node points to the next node only.
  • Doubly Linked List: Nodes have two pointers: one to the next and one to the previous node.
  • Circular Linked List: Last node points back to the first node, forming a loop.
  • Doubly Circular Linked List: Combines both circular and doubly linked lists.

Each type has different use-cases based on traversal and memory needs. For instance, doubly linked lists allow easy backward traversal at the cost of extra pointers.

3) How do you reverse a Singly Linked List? (Coding Approach)

Reversing a linked list is a classic interview question. The goal is to change the direction of the pointers so that the list is reversed in place without allocating new nodes.

Key Idea:
Use three pointers — prev, curr, and next — and iterate through the list. At each step, redirect curr.next to prev, then advance all pointers.

ListNode reverseList(ListNode head) {
    ListNode prev = null;
    ListNode curr = head;
    while (curr != null) {
        ListNode next = curr.next;
        curr.next = prev;
        prev = curr;
        curr = next;
    }
    return prev; // New head
}

This transforms the linked structure without extra space and runs in O(n) time.

4) Explain the Two-Pointer Technique to Find the Middle of a Linked List.

The most efficient way to find the middle node of a linked list is using two pointers:

  • A slow pointer moves one node at a time.
  • A fast pointer moves two nodes at a time.

When the fast pointer reaches the end, the slow pointer will be at the midpoint. This technique operates in O(n) time without additional space.

5) How would you detect a cycle in a Linked List?

Cycle detection is another classic problem. The standard solution uses Floyd’s Tortoise and Hare Algorithm:

  • Move slow pointer one step at a time.
  • Move fast pointer two steps at a time.
  • If the list has a cycle, the two pointers will meet.

If the fast pointer reaches null, the list has no cycle. This method runs in O(n) time and O(1) space.

6) What are the advantages and disadvantages of Linked Lists?

Linked lists offer several benefits and trade-offs:

Advantages Disadvantages
Dynamic size No random access
Easy insert/delete Extra memory for pointers
Efficient for growing data Poor cache performance

Linked lists perform well for dynamic data but may be slower than arrays for element access because each access requires traversal from the head.

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7) How do you merge two sorted linked lists?

Merging two sorted lists is another common interview problem. The idea is to traverse both lists simultaneously and build a new sorted list by selecting the smaller node from either list at each step.

ListNode mergeTwoLists(ListNode l1, ListNode l2) {
    ListNode dummy = new ListNode(0);
    ListNode tail = dummy;
    while (l1 != null && l2 != null) {
        if (l1.val < l2.val) {
            tail.next = l1;
            l1 = l1.next;
        } else {
            tail.next = l2;
            l2 = l2.next;
        }
        tail = tail.next;
    }
    tail.next = (l1 != null) ? l1 : l2;
    return dummy.next;
}

This method preserves sorted order and runs in O(n + m) time for lists of lengths n and m.

8) Explain how to delete the Nth node from the end of a Linked List.

The most efficient technique uses two pointers separated by n nodes. Advance the first pointer n steps, then move both pointers until the first reaches the end. The second pointer will then be just before the target node.

This avoids computing the list length separately and completes in O(n) time. It also handles edge cases like removing the first node.

9) What is the time complexity to access the k-th element in a linked list?

Accessing the kth element in a linked list requires traversal from the head until you reach the kth node. Because linked lists provide no direct indexing, this costs O(n) time in the worst case.

In contrast, arrays support direct indexing in O(1) time.

10) Why would you use a Linked List instead of an Array?

Linked lists are especially useful when:

  • You expect frequent insertions and deletions at arbitrary positions.
  • You do not know the size of your data in advance.
  • Memory fragmentation makes contiguous memory allocation difficult.

They support efficient dynamic memory allocation and constant-time insertion/deletion at list ends or with a known node reference—advantages that arrays cannot match.

11) What are the real-world applications of Linked Lists?

Linked lists are widely used in systems where dynamic memory allocation, frequent insertions, or variable-size data structures are required. They are implemented in several core computer science concepts and applications such as:

  • Dynamic memory management (used in operating systems)
  • Undo/Redo functionalities in text editors
  • Hash table chaining to resolve collisions
  • Music or video playlist navigation
  • Graph adjacency representation
  • Polynomial arithmetic operations

These examples highlight how linked lists provide flexibility and efficient manipulation of sequences where array resizing would be expensive.

12) Explain the difference between a singly and a doubly linked list.

Feature Singly Linked List Doubly Linked List
Pointers 1 (next node only) 2 (previous and next)
Traversal One direction only Both directions
Memory Usage Less (only one pointer) More (extra pointer)
Deletion Harder (need previous node) Easier
Example Use Stack implementation Browser history navigation

A doubly linked list is more versatile but consumes additional memory. In contrast, singly linked lists are lightweight and efficient for unidirectional traversal.

13) How do you remove duplicates from a sorted linked list?

When a linked list is already sorted, duplicates will be adjacent.

Traverse the list and compare each node’s data with its next node. If they match, skip the next node.

void removeDuplicates(ListNode head) {
    ListNode current = head;
    while (current != null && current.next != null) {
        if (current.val == current.next.val) {
            current.next = current.next.next;
        } else {
            current = current.next;
        }
    }
}

Complexity: O(n) time and O(1) space.

For unsorted lists, a HashSet can be used to track seen values.

14) What is the difference between a linear and circular linked list?

Feature Linear Linked List Circular Linked List
Last Node Points to NULL Points to head node
Traversal Ends when next == NULL Continuous traversal
Use Case Stack, Queue Round-robin scheduling
Complexity Simpler More complex handling

Circular lists are particularly beneficial in applications such as CPU scheduling, where processes are cyclically executed.

15) How do you find the intersection point of two linked lists?

To determine if two singly linked lists intersect:

  1. Find the lengths of both lists.
  2. Advance the pointer of the longer list by the difference in lengths.
  3. Traverse both lists simultaneously until the nodes are identical.

Alternatively, a HashSet can be used to store visited nodes for O(n) space.

This approach is efficient and commonly asked in senior-level interviews.

16) How do you check if two linked lists are identical?

Two linked lists are identical if:

  • They have the same number of nodes.
  • The corresponding node values are identical in order.

Algorithm:

  1. Traverse both lists together.
  2. Compare each node’s data.
  3. If all pairs match and both reach NULL, they are identical.

Time complexity: O(n)

Space complexity: O(1)

17) What is a memory leak in the context of linked lists?

A memory leak occurs when dynamically allocated nodes are not freed after use.

In linked lists, if delete or free() is not called on nodes removed from the list, memory remains occupied even though it is no longer accessible.

For instance, failing to release deleted nodes in C/C++ leads to gradual memory exhaustion, causing system slowdown or crashes.

Proper cleanup using a destructor or explicit deallocation avoids this problem.

18) Explain how to implement a stack using a linked list.

In a stack, elements follow the LIFO (Last In, First Out) order.

A linked list is ideal because insertions and deletions occur at the head efficiently.

Operations:

  • Push: Insert new node at head.
  • Pop: Remove node from head.
  • Peek: Return head data.

Advantages:
No need for a fixed size array; grows dynamically as elements are pushed.

19) How can a linked list be used to implement a queue?

In a queue, elements follow the FIFO (First In, First Out) order.

Use a linked list where:

  • Enqueue (Insert): Add node at the tail.
  • Dequeue (Remove): Delete node from the head.

This allows both operations in O(1) time with two pointers — front and rear.

It is commonly used in process scheduling and printer queue systems.

20) What are the differences between an array list and a linked list in Java?

Aspect ArrayList LinkedList
Storage Dynamic array Doubly linked list
Access time O(1) O(n)
Insert/Delete Costly in middle Efficient at ends
Memory Overhead Less More (extra pointers)
Use Case Frequent access Frequent insertion/deletion

Example: Use ArrayList for lookup-heavy operations, and LinkedList when insertion/deletion operations dominate.

21) How do you flatten a multilevel linked list?

A multilevel linked list may contain nodes that have both next and child pointers (each child leading to another linked list). The goal is to flatten all nodes into a single-level linked list.

Approach:

  1. Use a stack or recursive function.
  2. Start from the head node.
  3. If a node has a child, push its next node to the stack, and make child as next.
  4. Continue until stack is empty.

Time Complexity: O(n)

Space Complexity: O(n) for recursion/stack.

Example (conceptually):

1 - 2 - 3
    |
    4 - 5
Flattened → 1 → 2 → 4 → 5 → 3

This question evaluates your understanding of recursion and pointer manipulation.

22) How do you clone a linked list with random pointers?

Each node in this special linked list has two pointers:

  • next → points to the next node.
  • random → points to any arbitrary node.

Algorithm (3 steps):

  1. Insert cloned nodes between original nodes.
  2. Assign random pointers for clones (clone.random = original.random.next).
  3. Separate the two lists.

This avoids extra space for a hash map and runs in O(n) time with O(1) extra space.

Use Case: Deep copying complex data structures (e.g., graphs or object references).

23) What is a skip list, and how is it related to linked lists?

A skip list is a layered linked list structure that allows fast search, insertion, and deletion (similar to balanced trees).

Operation Average Time Worst Case
Search O(log n) O(n)
Insert/Delete O(log n) O(n)

It contains multiple levels, where upper levels “skip” several nodes, improving search efficiency.

Example: Used in databases like Redis and concurrent map implementations.

24) How can you detect a palindrome in a linked list?

A linked list is a palindrome if it reads the same backward and forward.

Algorithm:

  1. Find the middle of the list.
  2. Reverse the second half.
  3. Compare the two halves node by node.

If all corresponding nodes match, it is a palindrome.

Example:

1 → 2 → 3 → 2 → 1 → ✅ Palindrome

1 → 2 → 3 → 4 → ❌ Not a palindrome

Time Complexity: O(n)

Space Complexity: O(1)

25) How do you remove the loop in a linked list?

If a loop exists (using Floyd’s cycle detection), remove it using these steps:

  1. Detect the meeting point of slow and fast pointers.
  2. Move one pointer to the head.
  3. Move both pointers one step at a time until they meet at the loop starting node.
  4. Set the previous node’s next to null.

This approach ensures no extra memory usage while resolving cycles.

26) What are the different ways to represent linked lists in memory?

Linked lists can be represented in three main ways:

Representation Type Description Example Use
Dynamic nodes Each node dynamically allocated and linked C, C++
Static array representation Uses array indices instead of pointers Embedded systems
Linked objects Object-oriented representation with classes Java, Python

Each approach suits different environments — for example, array-based lists are used when pointer manipulation is restricted.

27) How can you find the length of a linked list (iterative and recursive)?

Iterative Approach:

int getLength(ListNode head) {
    int count = 0;
    while (head != null) {
        count++;
        head = head.next;
    }
    return count;
}

Recursive Approach:

int getLength(ListNode head) {
    if (head == null) return 0;
    return 1 + getLength(head.next);
}

Both approaches have O(n) time complexity; recursion adds O(n) space overhead due to call stack.

28) Explain the concept of circular doubly linked lists with an example.

In a circular doubly linked list, each node has two links — one to the next and one to the previous — and the last node’s next points to the head, while the head’s prev points to the last node.

Example Use Cases:

  • Real-time operating systems (round-robin scheduling)
  • Music playlist looping
  • Navigation between tabs or slides

Advantages:

  • Bidirectional traversal.
  • No null references.
  • Efficient insertions and deletions.

29) How do you delete alternate nodes in a linked list?

Algorithm:

  1. Start from the head.
  2. Delete every second node by adjusting pointers.
  3. Continue until the list ends.

Example:

Input: 1 → 2 → 3 → 4 → 5  
Output: 1 → 3 → 5

Complexity:

  • Time: O(n)
  • Space: O(1)

This checks the understanding of pointer traversal and deletion safety.

30) How can you find the nth node from the beginning and from the end of a linked list?

From the beginning: Traverse the list until count = n.

From the end: Use two pointers.

  1. Move the first pointer n steps ahead.
  2. Move both simultaneously until the first reaches null.
  3. The second pointer now points to the nth node from the end.

Time Complexity: O(n)

Space Complexity: O(1)

This approach avoids calculating length separately, improving efficiency.

31) How do you reorder a linked list?

The problem: Given a list L0 → L1 → … → Ln-1 → Ln, reorder it as L0 → Ln → L1 → Ln-1 → L2 → Ln-2 → …

Steps:

  1. Find the middle of the list.
  2. Reverse the second half.
  3. Merge the two halves alternately.

Example:

Input: 1 → 2 → 3 → 4 → 5  
Output: 1 → 5 → 2 → 4 → 3

Complexity: O(n) time, O(1) space.

This tests multiple linked list operations in one question.

32) How do you partition a linked list around a given value x?

Objective:
Rearrange nodes so that all nodes less than x come before nodes greater than or equal to x.

Approach:

  • Maintain two dummy lists: before and after.
  • Traverse original list and append nodes to respective lists.
  • Combine them at the end.

Example:

Input: 3 → 5 → 8 → 5 → 10 → 2 → 1, x = 5  
Output: 3 → 2 → 1 → 5 → 8 → 5 → 10

This is frequently asked to evaluate data rearrangement ability.

33) How do you sort a linked list?

Since linked lists do not support random access, Merge Sort is the best choice.

Steps:

  1. Split the list into halves using slow/fast pointers.
  2. Recursively sort each half.
  3. Merge sorted halves.

Advantages:

  • O(n log n) time.
  • O(1) extra space (for iterative version).

Unlike arrays, QuickSort is inefficient for linked lists due to pointer rearrangement complexity.

34) What is the difference between singly, doubly, and circular linked lists?

Feature Singly Doubly Circular
Links One (next) Two (prev & next) Last node connects to head
Traversal Forward only Forward & backward Infinite traversal possible
Insertion/Deletion Moderate Easier at both ends Special case handling
Use Case Stack, Queue Undo operations Round-robin scheduling

This comparison question often appears to check conceptual clarity.

35) How do you find the intersection node of two circular linked lists?

This is an extension of the intersection problem.

Algorithm:

  1. Detect if each list has a loop.
  2. If both are acyclic → use the standard intersection algorithm.
  3. If both are cyclic → find the loop start for each and check if they are the same or connected.

This problem combines cycle detection and intersection logic, testing multi-concept reasoning.

36) Explain how to insert a node in a sorted linked list.

Steps:

  1. Create a new node with the given value.
  2. Traverse until you find the correct position.
  3. Adjust next pointers accordingly.

Example:

Input: 1 → 3 → 5 → 7, Insert 4  
Output: 1 → 3 → 4 → 5 → 7

This is a basic manipulation problem to test pointer adjustment understanding.

37) How do you split a linked list into two halves?

Algorithm:

  • Use the slow and fast pointer method.
  • When fast reaches the end, slow will be at the midpoint.
  • Split at that node.

Example:

Input: 1 → 2 → 3 → 4 → 5  
Output: 1 → 2 → 3  and  4 → 5

This operation is often the first step of linked list merge sort.

38) How do you find the last occurrence of a value in a linked list?

Traverse through the list while keeping track of the last node where the target value is found.

Pseudo-code:

ListNode findLastOccurrence(ListNode head, int val) {
    ListNode result = null;
    while (head != null) {
        if (head.val == val) result = head;
        head = head.next;
    }
    return result;
}

Complexity: O(n)

This checks the understanding of linear traversal and condition checking.

39) How can you remove all occurrences of a given key from a linked list?

Algorithm:

  1. Handle head nodes first if they contain the target key.
  2. Then traverse and delete subsequent nodes containing the key.

Example:

Input: 1 → 2 → 6 → 3 → 4 → 5 → 6, Key = 6  
Output: 1 → 2 → 3 → 4 → 5

Complexity: O(n)

This demonstrates knowledge of edge cases (especially head deletions).

40) What are the key differences between stack and linked list data structures?

Feature Stack Linked List
Access Type LIFO (Last In, First Out) Sequential
Implementation Array or Linked List Node-based
Operations Push/Pop Insert/Delete/Traverse
Flexibility Restricted access Flexible access
Use Case Function call management Dynamic data handling

A stack can be implemented using a linked list, but they differ in concept — stack has restricted access while linked list is a general-purpose structure.

🔍 Top Linked List Interview Questions with Real-World Scenarios & Strategic Responses

1) What is a linked list, and how does it differ from an array?

Expected from candidate: The interviewer wants to assess your understanding of fundamental data structures and your ability to compare trade-offs.

Example answer: A linked list is a linear data structure where elements, called nodes, are connected using pointers. Each node contains data and a reference to the next node. Unlike arrays, linked lists do not require contiguous memory and allow dynamic resizing, but they have slower access times because elements are not indexed.

2) When would you choose a linked list over an array in a real-world application?

Expected from candidate: They are evaluating your practical judgment in selecting appropriate data structures.

Example answer: I would choose a linked list when frequent insertions and deletions are required, especially in the middle of the data set. In my previous role, I worked on a task scheduling feature where tasks were frequently added and removed, and a linked list provided better performance than an array.

3) Can you explain the difference between singly linked lists and doubly linked lists?

Expected from candidate: The interviewer wants to verify your conceptual clarity and ability to explain technical differences clearly.

Example answer: A singly linked list has nodes that point only to the next node, while a doubly linked list has nodes that point to both the next and previous nodes. Doubly linked lists allow easier backward traversal but require more memory due to the additional pointer.

4) How would you detect a cycle in a linked list?

Expected from candidate: This tests your problem-solving skills and familiarity with common algorithmic patterns.

Example answer: A common approach is to use two pointers moving at different speeds, often called the slow and fast pointer technique. If there is a cycle, the two pointers will eventually meet. At a previous position, I used this approach to prevent infinite loops in a data processing pipeline.

5) What are some common operations performed on linked lists?

Expected from candidate: The interviewer wants to see if you understand standard operations and their implications.

Example answer: Common operations include insertion, deletion, traversal, searching, and reversing the list. Each operation has different time complexities depending on where it is performed, which is important when designing efficient systems.

6) How do you handle inserting a node in the middle of a linked list?

Expected from candidate: They are checking your understanding of pointer manipulation and attention to detail.

Example answer: To insert a node in the middle, I first traverse the list to find the target position, then adjust the pointers so the new node points to the next node and the previous node points to the new node. Careful pointer updates are critical to avoid breaking the list.

7) Describe a situation where a linked list caused performance issues and how you addressed it.

Expected from candidate: This behavioral question evaluates your ability to reflect and optimize.

Example answer: At my previous job, a linked list was used for frequent search operations, which led to slow performance. I identified the issue and recommended switching to a hash-based structure, significantly improving lookup times.

8) How would you reverse a linked list?

Expected from candidate: The interviewer is testing your logical thinking and understanding of iterative or recursive approaches.

Example answer: I would reverse a linked list by iterating through it and changing each node’s next pointer to point to the previous node. This process continues until all pointers are reversed and the head is updated.

9) What are the advantages and disadvantages of using linked lists?

Expected from candidate: They want a balanced perspective and awareness of trade-offs.

Example answer: The advantages include dynamic size and efficient insertions and deletions. The disadvantages include higher memory usage and slower access times compared to arrays. In my last role, understanding these trade-offs helped in choosing the right structure for different components.

10) How do you decide which type of linked list to use in a system design?

Expected from candidate: This situational question assesses decision-making in architectural contexts.

Example answer: I consider factors such as traversal needs, memory constraints, and operation frequency. For example, if backward traversal is required, a doubly linked list is more suitable, while a singly linked list is sufficient for simpler, memory-efficient implementations.

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