Core Technical Computer Science MCQs Practice Questions & Worked Solutions

Q1 Easy • Amazon, Zoho

Which of the following data structures has constant average time complexity O(1) for search, insert, and delete operations?

A Binary Search Tree

B AVL Tree

C Hash Table

D B-Tree

Q2 Medium • Google, Microsoft

What is the worst-case time complexity of the QuickSort algorithm?

A O(n log n)

B O(n)

C O(n²)

D O(log n)

Q3 Easy • Amazon, Microsoft

Which data structure is primarily used to implement Breadth-First Search (BFS) on a graph?

A Stack

B Queue

C Priority Queue

D Binary Search Tree

Q4 Medium • Intel, Qualcomm

Which of the following is NOT one of Coffman's four necessary conditions for a Deadlock to occur in an operating system?

A Mutual Exclusion

B Hold and Wait

C Preemption Allowed

D Circular Wait

Q5 Medium • Oracle, SAP

In a relational database, what normal form requires that every non-prime attribute be fully functionally dependent on the entire primary key, eliminating partial dependencies?

A First Normal Form (1NF)

B Second Normal Form (2NF)

C Third Normal Form (3NF)

D Boyce-Codd Normal Form (BCNF)

Q6 Easy • Cisco, Juniper

In the TCP 3-way handshake, what is the correct sequence of packet flags exchanged between client and server?

A ACK → SYN → SYN-ACK

B SYN → SYN-ACK → ACK

C SYN → ACK → SYN-ACK

D SYN-ACK → SYN → ACK

Q7 Medium • Google, Amazon

What is the maximum number of nodes in a binary tree of height 'h' (where height of root node is 0)?

A 2^h

B 2^(h+1) - 1

C 2^h - 1

D 2^(h-1)

Q8 Easy • Microsoft, Red Hat

Which process scheduling algorithm can suffer from the 'Convoy Effect'?

A Round Robin

B First-Come, First-Served (FCFS)

C Shortest Job First (SJF)

D Priority Scheduling

Q9 Medium • Thoughtworks, Amazon

In Object-Oriented Programming, which principle states that 'Derived classes must be substitutable for their base classes without altering the correctness of the program'?

A Single Responsibility Principle

B Open/Closed Principle

C Liskov Substitution Principle

D Dependency Inversion Principle

Q10 Medium • Amazon, Microsoft

What is the average and worst-case time complexity of searching for an element in a balanced Binary Search Tree (AVL or Red-Black Tree) containing N nodes?

A O(1)

B O(log N)

C O(N)

D O(N log N)

Q11 Easy • TCS, Accenture

Which SQL constraint uniquely identifies each record in a database table while strictly disallowing NULL values?

A UNIQUE

B FOREIGN KEY

C PRIMARY KEY

D CHECK

Q12 Easy • Cisco, Juniper

In the OSI 7-Layer Reference Model, which layer is responsible for logical IP addressing and packet routing across intermediate subnets?

A Data Link Layer (Layer 2)

B Network Layer (Layer 3)

C Transport Layer (Layer 4)

D Session Layer (Layer 5)

Q13 Easy • Thoughtworks, Amazon

In Git version control, which command creates a new branch named 'feature-auth' and immediately checks out into it?

A git branch feature-auth

B git checkout -b feature-auth

C git merge feature-auth

D git commit -b feature-auth

Q14 Easy

A program must undo the most recently completed action first. Which data structure directly matches this removal order?

A Stack

B Min-heap

C Unordered set

D Queue

Q15 Easy

How many distinct bit patterns can an 8-bit unsigned integer represent?

A 256

B 255

C 512

D 128

Q16 Easy

Which Git command reports the current branch and the state of tracked and untracked files without staging them?

A git add .

B git status

C git commit

D git reset --hard

Q17 Medium

A SQL table contains three rows whose score values are 10, NULL, and 20. What does SELECT COUNT(score) return?

A 2

B 3

C 1

D 0

Q18 Medium

An API has authenticated a user, but its policy refuses that user access to a resource. Which HTTP status most directly expresses the refusal when the server chooses to disclose it?

A 403 Forbidden

B 401 Unauthorized

C 301 Moved Permanently

D 201 Created

Q19 Medium

Two threads need locks A and B. Which rule directly removes circular wait for these two locks?

A Every thread sleeps before locking

B Each thread holds its first lock until the other becomes available

C Every thread acquires A before B

D Each thread acquires whichever lock is free first

Q20 Medium

What property does correctly validated HTTPS server authentication primarily establish for a browser connection?

A The user has permission to every resource

B The server proves control of credentials valid for the requested hostname

C The website has no application vulnerabilities

D Every page statement is factually correct

Core Technical Computer Science MCQs Practice Questions (20)