Top 100+ Most asked Computer Science Engineering Interview Questions for Job Preparation

  by Vishesh Namdev    01-01-2025

Designed for aspiring software engineers and developers, this category features questions on data structures, algorithms, object-oriented programming, and system design. It includes coding challenges and real-world scenarios to test your problem-solving abilities. From C++ to Python, and from recursion to database management, these questions cover the essentials to help you excel in technical interviews.

100+ Computer Science Engineering Interview Questions - The Royal Coding

  1. 1. Data Structures & Algorithms

  2. Question: 1. Explain the difference between a stack and a queue.

    Answer: A stack is a LIFO (Last In, First Out) data structure, while a queue is a FIFO (First In, First Out) data structure.

  3. Question: 2. How does a hash table work, and what are common hashing techniques?

    Answer: A hash table stores key-value pairs and uses a hash function to compute an index for storing data. Common hashing techniques include division method, multiplication method, and universal hashing.

  4. Question: 3. What is the Big-O notation for a binary search algorithm?

    Answer: O(log n)

  5. Question: 4. Explain merge sort and its time complexity.

    Answer: Merge sort is a divide-and-conquer algorithm that splits the array, sorts each part, and merges them. Its time complexity is O(n log n).

  6. Question: 5. What is a heap? How does a min-heap differ from a max-heap?

    Answer: A heap is a complete binary tree. In a min-heap, the parent node is smaller than its children; in a max-heap, the parent node is larger.

  7. Question: 6. How would you reverse a linked list?

    Answer: By iterating through the list and changing the next pointers to point to the previous nodes.

  8. Question: 7. What are the differences between array and linked list?

    Answer: Arrays have fixed size and provide O(1) access, while linked lists are dynamic and have O(n) access time but allow O(1) insertions/deletions.

  9. Question: 8. What is dynamic programming, and how is it different from recursion?

    Answer: Dynamic programming stores intermediate results to avoid redundant calculations, whereas recursion solves problems by repeatedly breaking them into smaller subproblems.

  10. Question: 9. Describe the concept of a binary search tree (BST).

    Answer: A BST is a binary tree where each node has a key, and the left subtree contains keys smaller than the root, while the right subtree contains keys larger.

  11. Question: 10. How would you implement Dijkstra's algorithm for finding the shortest path?

    Answer: By using a priority queue to repeatedly select the vertex with the smallest distance and updating the distances of its neighbors.

  12. Question: 11. What is the difference between DFS and BFS in graph traversal?

    Answer: DFS explores as far as possible along a branch before backtracking, while BFS explores all neighbors before moving deeper.

  13. Question: 12. Can a stack be used to implement a queue? How?

    Answer: Yes, using two stacks: one for enqueuing and one for dequeuing.

  14. Question: 13. How would you handle collision in a hash table?

    Answer: By using chaining (linked lists) or open addressing (linear probing, quadratic probing, double hashing).

  15. Question: 14. Explain the time complexity of insertion in an AVL tree.

    Answer: O(log n)

  16. Question: 15. How would you detect a cycle in a directed graph?

    Answer: By using Depth First Search (DFS) with a visited and recursion stack.

  17. Question: 16. Explain Kruskal's algorithm and its use in finding minimum spanning trees.

    Answer: Kruskal's algorithm sorts all edges and adds them one by one to the spanning tree, ensuring no cycles.

  18. Question: 17. What is the significance of the KMP algorithm in string matching?

    Answer: The KMP algorithm efficiently finds patterns in a string by preprocessing the pattern to avoid unnecessary comparisons.

  19. Question: 18. How do you check if a binary tree is balanced?

    Answer: By ensuring the height difference between left and right subtrees for every node is at most 1.

  20. Question: 19. What is tail recursion?

    Answer: Tail recursion occurs when the recursive call is the last operation in the function.

  21. Question: 20. Differentiate between greedy algorithms and dynamic programming.

    Answer: Greedy algorithms make locally optimal choices, while dynamic programming solves problems by considering all possibilities and using overlapping subproblems.

  22. Question: 21. How do you implement a priority queue using a heap?

    Answer: By using a binary heap where the root is always the highest (max-heap) or lowest (min-heap) priority element.

  23. Question: 22. Explain the concept of memoization in dynamic programming.

    Answer: Memoization stores results of expensive function calls to avoid redundant computations.

  24. Question: 23. Describe the quick sort algorithm and its average and worst-case time complexities.

    Answer: Quick sort partitions the array into two parts and sorts them recursively. Average time complexity is O(n log n); worst-case is O(n^2).

  25. Question: 24. What is Amortized Time Complexity, and where is it used?

    Answer: It is the average time per operation over a sequence of operations. Used in dynamic arrays and hash tables.

  26. Question: 25. How would you find the kth largest element in an unsorted array?

    Answer: By using a heap or the Quickselect algorithm.

  27. 2. Operating Systems

  1. Question: 26. What is process scheduling? Explain different types of schedulers.

    Answer: Process scheduling determines the execution order of processes. Types include long-term, short-term, and medium-term schedulers.

  2. Question: 27. How does virtual memory work?

    Answer: Virtual memory uses disk space as an extension of RAM, allowing processes to execute beyond physical memory limits.

  3. Question: 28. Explain deadlock and how it can be prevented.

    Answer: Deadlock is a situation where processes wait indefinitely for resources. Prevention includes resource ordering and avoiding circular waits.

  4. Question: 29. What is the difference between process and thread?

    Answer: A process is an independent executing instance, while a thread is a lightweight unit of execution within a process.

  5. Question: 30. Describe the Round Robin scheduling algorithm.

    Answer: Round Robin assigns time slices to processes in a cyclic order, ensuring fair CPU time distribution.

  6. Question: 31. Explain the concept of paging and segmentation.

    Answer: Paging divides memory into fixed-size blocks, while segmentation divides it into variable-size logical segments.

  7. Question: 32. What are race conditions? How can they be avoided?

    Answer: Race conditions occur when multiple threads access shared resources simultaneously. They can be avoided using locks, mutexes, or semaphores.

  8. Question: 33. How does the banker's algorithm prevent deadlock?

    Answer: The banker's algorithm ensures resources are allocated safely by checking if allocation would leave the system in a safe state.

  9. Question: 34. Explain the difference between preemptive and non-preemptive scheduling.

    Answer: Preemptive scheduling allows process interruption, while non-preemptive scheduling completes a process before switching.

  10. Question: 35. What is a system call, and how does it work?

    Answer: A system call is a user-space request to the kernel for services like file operations or process control.

  11. Question: 36. Describe the difference between multitasking and multithreading.

    Answer: Multitasking runs multiple processes, while multithreading runs multiple threads within a process.

  12. Question: 37. What is context switching? When does it occur?

    Answer: Context switching is saving a process state and restoring another. It occurs during process scheduling or interrupts.

  13. Question: 38. What is the purpose of a mutex in process synchronization?

    Answer: A mutex ensures only one thread accesses a critical section at a time to prevent race conditions.

  14. Question: 39. Explain inter-process communication (IPC).

    Answer: IPC allows processes to exchange data using mechanisms like shared memory, message passing, or pipes.

  15. Question: 40. What are the differences between monolithic kernels and microkernels?

    Answer: Monolithic kernels manage all OS functions, while microkernels handle core services, delegating others to user space.

  16. Question: 41. How does demand paging work in virtual memory?

    Answer: Demand paging loads pages into memory only when needed, reducing memory usage.

  17. Question: 42. What are inodes in file systems?

    Answer: Inodes store metadata about files, like size, permissions, and disk block locations.

  18. Question: 43. What is the difference between paging and swapping in memory management?

    Answer: Paging moves memory pages between RAM and disk, while swapping moves entire processes.

  19. Question: 44. Describe thrashing and how it can be avoided.

    Answer: Thrashing occurs when excessive paging reduces performance. It can be avoided by allocating sufficient memory or adjusting multiprogramming levels.

  20. Question: 45. How do signal handlers work in UNIX/Linux systems?

    Answer: Signal handlers execute specific functions when a process receives a signal, overriding default behavior.

  21. Question: 46. What is scheduling starvation, and how can it be resolved?

    Answer: Starvation occurs when low-priority processes are indefinitely delayed. It can be resolved using aging to increase priority over time.

  22. Question: 47. Explain the concept of priority inversion and its solution.

    Answer: Priority inversion occurs when a high-priority task waits for a lower-priority task. Solutions include priority inheritance.

  23. Question: 48. What is the role of a scheduler in an operating system?

    Answer: The scheduler manages CPU allocation to processes, optimizing performance and resource utilization.

  24. Question: 49. How does process synchronization prevent race conditions?

    Answer: Process synchronization uses mechanisms like locks, semaphores, and monitors to ensure safe shared resource access.

  25. Question: 50. What are the different states of a process lifecycle?

    Answer: Process states include new, ready, running, waiting, and terminated.

  26. 3. Databases

  27. Question: 51. What is normalization, and why is it important?

    Answer: Normalization organizes data to reduce redundancy and improve data integrity.

  28. Question: 52. Explain ACID properties in databases.

    Answer: ACID stands for Atomicity, Consistency, Isolation, and Durability, ensuring reliable transactions.

  29. Question: 53. What is a foreign key? How does it differ from a primary key?

    Answer: A foreign key links tables and references a primary key in another table; a primary key uniquely identifies a record.

  30. Question: 54. What is the difference between SQL and NoSQL databases?

    Answer: SQL databases are relational and use structured schemas, while NoSQL databases are non-relational and handle unstructured data.

  31. Question: 55. How would you optimize a slow-running SQL query?

    Answer: By indexing, analyzing query plans, optimizing joins, and avoiding SELECT *.

  32. Question: 56. Explain transaction isolation levels in databases.

    Answer: Isolation levels (READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ, SERIALIZABLE) define how transactions interact with each other.

  33. Question: 57. What are triggers and when would you use them?

    Answer: Triggers are automatic actions executed in response to certain database events.

  34. Question: 58. Explain the concept of indexing and how it improves database performance.

    Answer: Indexing creates a data structure to allow faster search and retrieval.

  35. Question: 59. How does database partitioning work?

    Answer: Partitioning divides data into smaller segments for improved manageability and performance.

  36. Question: 60. What is a JOIN in SQL, and what are the different types of joins?

    Answer: JOIN combines data from multiple tables. Types include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN.

  37. Question: 61. What is a view in a database? How is it different from a table?

    Answer: A view is a virtual table based on a query, whereas a table physically stores data.

  38. Question: 62. Explain the difference between HAVING and WHERE clauses in SQL.

    Answer: WHERE filters rows before aggregation; HAVING filters after aggregation.

  39. Question: 63. What are stored procedures? How do they differ from functions?

    Answer: Stored procedures perform tasks and can return multiple values, while functions return a single value.

  40. Question: 64. Explain the concept of sharding in distributed databases.

    Answer: Sharding partitions data across multiple servers for scalability.

  41. Question: 65. How does deadlock occur in databases? How can it be resolved?

    Answer: Deadlock occurs when transactions wait indefinitely for resources. It can be resolved by timeouts or deadlock detection algorithms.

  42. Question: 66. What is a schema in a database?

    Answer: A schema defines the structure of a database, including tables, columns, and relationships.

  43. Question: 67. How do cascading deletes work in relational databases?

    Answer: Cascading deletes automatically remove dependent rows when a referenced row is deleted.

  44. Question: 68. What is denormalization, and when is it beneficial?

    Answer: Denormalization combines tables to improve read performance, often used in analytics.

  45. Question: 69. How would you implement pagination in a SQL query?

    Answer: By using LIMIT and OFFSET or ROW_NUMBER.

  46. Question: 70. What are database locks, and what are their types?

    Answer: Locks prevent concurrent access issues. Types include shared, exclusive, and row-level locks.

  47. Question: 71. What are aggregate functions in SQL? Give examples.

    Answer: Aggregate functions perform calculations on multiple rows. Examples: COUNT(), AVG(), MAX(), MIN(), SUM().

  48. Question: 72. How would you enforce referential integrity in a relational database?

    Answer: By using foreign keys with constraints like ON DELETE and ON UPDATE.

  49. Question: 73. Explain the differences between horizontal and vertical scaling in databases.

    Answer: Horizontal scaling adds more servers; vertical scaling increases server capacity.

  50. Question: 74. How does replication work in databases?

    Answer: Replication copies data from one server to others for redundancy and scalability.

  51. 4. Object-Oriented Programming (OOP)

  52. Question: 75. What is inheritance in OOP? Explain with an example.

    Answer: Inheritance allows one class to derive properties and behaviors from another. Example: A Dog class inherits from an Animal class.

  53. Question: 76. What is the difference between polymorphism and overloading?

    Answer: Polymorphism allows one interface with multiple implementations; overloading defines multiple methods with the same name but different parameters.

  54. Question: 77. How do abstract classes differ from interfaces?

    Answer: Abstract classes can have implementations; interfaces only define methods without implementation.

  55. Question: 78. Explain the concept of encapsulation in OOP.

    Answer: Encapsulation restricts direct access to an object's data, exposing only necessary parts.

  56. Question: 79. What is constructor chaining in object-oriented programming?

    Answer: Constructor chaining occurs when one constructor calls another in the same or a parent class.

  57. Question: 80. How would you implement multiple inheritance in a language that doesn't support it directly (e.g., Java)?

    Answer: By using interfaces.

  58. Question: 81. What is the diamond problem, and how is it resolved?

    Answer: The diamond problem occurs with multiple inheritance when a class inherits the same base class via different paths. It is resolved using virtual inheritance or interfaces.

  59. Question: 82. Explain method overriding and how it differs from overloading.

    Answer: Overriding changes a method's behavior in a subclass; overloading defines multiple methods with the same name but different parameters.

  60. Question: 83. What are design patterns? Give an example of a singleton pattern.

    Answer: Design patterns are reusable solutions to common problems. Singleton ensures a class has only one instance.

  61. Question: 84. Explain the SOLID principles of object-oriented design.

    Answer: SOLID principles ensure maintainable and scalable OOP designs: Single Responsibility, Open-Closed, Liskov Substitution, Interface Segregation, Dependency Inversion.

  62. Question: 85. What is the difference between aggregation and composition in OOP?

    Answer: Composition implies ownership and lifecycle management; aggregation does not.

  63. Question: 86. How does late binding work in polymorphism?

    Answer: Late binding resolves method calls at runtime, allowing dynamic method invocation.

  64. Question: 87. Explain dependency injection and its benefits.

    Answer: Dependency injection provides objects their dependencies, improving testability and modularity.

  65. Question: 88. What are access modifiers in OOP? Explain the difference between public, private, and protected.

    Answer: Access modifiers control visibility. Public: accessible everywhere; Private: within the class; Protected: within the class and subclasses.

  66. Question: 89. How is exception handling implemented in OOP languages?

    Answer: Using try-catch blocks, custom exceptions, and finally blocks.

  67. Question: 90. What is a virtual function, and why is it used?

    Answer: A virtual function allows method overriding in derived classes for runtime polymorphism.

  68. Question: 91. What is the Liskov Substitution Principle?

    Answer: Subtypes must be substitutable for their base types without altering functionality.

  69. Question: 92. How does garbage collection work in OOP languages like Java?

    Answer: Garbage collection automatically reclaims memory by identifying and removing unused objects.

  70. Question: 93. What is the difference between shallow copy and deep copy of objects?

    Answer: Shallow copy copies references, not objects; deep copy duplicates objects entirely.

  71. Question: 94. What is static binding, and when does it occur?

    Answer: Static binding occurs at compile time, binding methods to calls based on the declared type.

  72. Question: 95. What is duck typing in object-oriented languages?

    Answer: Duck typing determines object compatibility based on methods and properties rather than inheritance.

  73. 5. Networking

  74. Question: 96. What is the OSI model? Explain each layer.

    Answer: The OSI model has 7 layers: Physical, Data Link, Network, Transport, Session, Presentation, Application, each handling specific network functions.

  75. Question: 97. What is the difference between TCP and UDP?

    Answer: TCP is connection-oriented and reliable; UDP is connectionless and faster but less reliable.

  76. Question: 98. How does HTTP work, and what are HTTP status codes?

    Answer: HTTP is a request-response protocol. Status codes indicate the response type (e.g., 200 OK, 404 Not Found).

  77. Question: 99. What is DNS and how does it resolve domain names?

    Answer: DNS translates domain names to IP addresses using a hierarchical lookup.

  78. Question: 100. Explain the concept of IP addressing and subnetting.

    Answer: IP addressing assigns unique identifiers; subnetting divides networks into smaller segments for efficient use.

  79. Question: 101. What is ARP (Address Resolution Protocol)?

    Answer: ARP maps IP addresses to MAC addresses in a local network.

  80. Question: 102. Explain the difference between IPv4 and IPv6.

    Answer: IPv4 uses 32-bit addresses; IPv6 uses 128-bit addresses and offers better scalability and security.

  81. Question: 103. What are the differences between firewall and proxy?

    Answer: A firewall filters network traffic; a proxy acts as an intermediary for requests.

  82. Question: 104. What is SSL/TLS, and how does it provide security?

    Answer: SSL/TLS encrypts data in transit for secure communication.

  83. Question: 105. What is the difference between a router and a switch?

    Answer: A router connects networks; a switch connects devices within a network.

  84. Question: 106. Explain the concept of network congestion control.

    Answer: Congestion control manages data flow to prevent overwhelming the network.

  85. Question: 107. What is NAT (Network Address Translation), and why is it used?

    Answer: NAT translates private IP addresses to a public IP, conserving IP addresses.

  86. Question: 108. Explain the role of load balancers in networking.

    Answer: Load balancers distribute traffic across multiple servers to ensure availability and performance.

  87. Question: 109. What is ICMP, and what is its purpose?

    Answer: ICMP diagnoses network issues, sending error messages (e.g., ping).

  88. Question: 110. What is the difference between a VPN and a VLAN?

    Answer: A VPN secures communication over the internet; a VLAN groups devices in a virtual network.