InterviewPrep

https://leetcode.com/discuss/post/7408325/ultimate-interview-preparation-roadmap-t-abjd/
🔥 WHY THIS POST?
Most tech companies today expect candidates to be strong in coding + CS fundamentals + system design.This post is designed to be a quick, high-impact revision sheet.

📌 CONTENTS
1. Frequently Asked Coding Problems — Topic-wise / Pattern-wise

2. Must-Know CS Fundamentals — OS / DBMS / CN / OOPS

3. 40 fresh, high-yield MCQs from OS, DBMS, CN, and DSA

✅ SECTION 1 — MOST IMPORTANT CODING TOPICS (Pattern-wise Revision)
Here are the core categories you must revise before any interview.
I intentionally kept <10 problems per topic for rapid revision.

🔷 ARRAY & STRING PATTERNS
Two Sum

Kadane’s Agorithm

Sliding Window Maximum

Merge Intervals

Longest Substring Without Repeating

Prefix Sum / Difference Array

Search in Rotated Sorted Array

KMP Pattern Matching

🔷 DYNAMIC PROGRAMMING (DP)
Climbing Stairs

House Robber I/II

Longest Increasing Subsequence

0/1 Knapsack

Longest Palindromic Substring

Edit Distance

Coin Change

Partition Equal Subset Sum

🔷 TREE & BINARY SEARCH TREE
Inorder / Preorder / Postorder

Lowest Common Ancestor

Diameter of Binary Tree

Balanced Binary Tree

Symmetric Tree

Binary Tree Right Side View

Validate BST

Level Order Traversal

🔷 GRAPH ALGORITHMS
BFS / DFS

Topological Sort

Cycle Detection (Directed/Undirected)

Dijkstra’s Algorithm

Union Find (Disjoint Set)

Minimum Spanning Tree

Number of Islands

Bipartite Graph Check

🔷 BIT MANIPULATION
XOR Tricks

Find Missing Number

Count Set Bits

Reverse Bits

Power of Two

Single Number I/II

Bitmask DP Basics

✅ SECTION 2 — MUST-KNOW CS FUNDAMENTALS (Interview Essentials)
🖥 OPERATING SYSTEMS (OS)
Process vs Thread

Scheduling Algorithms (FCFS, SJF, RR, Priority)

Deadlock (Detection, Avoidance, Prevention)

Paging & Segmentation

Page Replacement (LRU, FIFO, Optimal)

Critical Section Problem

Mutex vs Semaphore

Thrashing

🗄 DATABASE MANAGEMENT SYSTEM (DBMS)
Keys (Primary, Candidate, Foreign, Composite)

Normalization (1NF → BCNF)

Joins (Inner, Left, Right, Cross)

Indexing & B-Tree / B+ Tree

Transactions & ACID

Triggers, Views, Cursors

Serializability (Conflict / View)

🌐 COMPUTER NETWORKS (CN)
OSI vs TCP/IP model

Subnetting

TCP vs UDP

DNS, DHCP, HTTP/HTTPS, FTP, SMTP

Flow & Error Control

Switching & Routing

IPv4 vs IPv6

Network Devices (Hub, Switch, Router, Bridge)

OOPS CONCEPTS
Class & Objects

Inheritance (Types & Modes)

Polymorphism (Compile-time & Runtime)

Abstract Class vs Interface

Constructor, Destructor, Copy Constructor

Operator Overloading

Static Keyword

Virtual Functions

Exception Handling

Encapsulation & Abstraction

✅ SECTION 3 — HIGH-IMPACT MCQs
Below are 40 fresh, high-yield MCQs from OS, DBMS, CN, and DSA.

🖥 OPERATING SYSTEM — MCQs
Which of the following is not a type of OS?
A) Distributed OS B) Network OS C) Sequential OS D) Batch OS
👉 Answer: C

Which scheduling algorithm guarantees no starvation?
A) Priority Scheduling B) SJF C) Round Robin D) LJF
👉 Answer: C

Thrashing occurs due to
A) Too many interrupts B) Too many processes C) Excessive paging D) Low CPU
👉 Answer: C

Belady’s anomaly is seen in
A) LRU B) FIFO C) Optimal D) LFU
👉 Answer: B

A program in execution is called
A) Thread B) Process C) Job D) Task
👉 Answer: B

🗄 DBMS — MCQs
Which isolation level prevents dirty reads?
A) Read Uncommitted B) Read Committed C) Repeatable Read D) Serializable
👉 Answer: B, C, D

A minimal super key is called
A) Primary key B) Candidate key C) Foreign key D) Composite key
👉 Answer: B

Which join returns all rows of left table?
A) Inner Join B) Right Join C) Left Join D) Full Join
👉 Answer: C

Which index is balanced in height?
A) Hash Index B) B-Tree C) Bitmap Index D) Dense Index
👉 Answer: B

Which anomaly is solved by BCNF but not 3NF?
A) Insertion B) Deletion C) Transitive dependency D) Dependency preservation
👉 Answer: C

🌐 COMPUTER NETWORKS — MCQs
Which protocol resolves domain names to IPs?
A) DHCP B) DNS C) ARP D) FTP
👉 Answer: B

Which layer ensures reliable communication?
A) Network B) Transport C) Session D) Presentation
👉 Answer: B

Which of the following is connection-oriented?
A) UDP B) TCP C) ARP D) ICMP
👉 Answer: B

What is the default port for HTTPS?
A) 21 B) 80 C) 443 D) 110
👉 Answer: C

Which device breaks collision domains?
A) Hub B) Switch C) Repeater D) Bridge
👉 Answer: B

🧮 DATA STRUCTURES — MCQs
Minimum nodes in AVL tree of height h is
A) 2^h B) Fib(h+2)-1 C) h+1 D) h²
👉 Answer: B

Which structure supports O(1) average insert/delete at ends?
A) Queue B) Stack C) Deque D) List
👉 Answer: C

Which traversal prints BST in sorted order?
A) Preorder B) Inorder C) Postorder D) BFS
👉 Answer: B

Which data structure is used in Dijkstra’s algorithm?
A) Stack B) Priority Queue C) Set D) Deque
👉 Answer: B

Hash collisions are resolved by
A) Chaining B) Rehashing C) Open addressing D) All of the above
👉 Answer: D

🧵 SYSTEM DESIGN — MCQs
Which consistency model is strongest?
A) Eventual B) Causal C) Strong D) Weak
👉 Answer: C

CAP theorem states a distributed system can't have
A) Consistency B) Availability C) Partition tolerance D) All three
👉 Answer: D

CDN improves
A) Write latency B) Read latency C) Bandwidth D) Replication
👉 Answer: B

Load balancer helps with
A) Scaling B) Replication C) Logging D) Caching
👉 Answer: A

Sharding reduces
A) Single DB load B) Network traffic C) Cache misses D) CPU usage
👉 Answer: A

🔧 BIT MANIPULATION — MCQs
To check if a number is power of two:
A) x & (x+1) B) x | (x−1) C) x & (x−1) == 0 D) x >> 2
👉 Answer: C

XOR of a number with itself is
A) Number B) Zero C) One D) Undefined
👉 Answer: B

Which retrieves the rightmost set bit?
A) x & −x B) x | (x−1) C) x ^ (x−1) D) x >> 1
👉 Answer: A

Bitmask is used in
A) DP B) Graph C) String D) Heap
👉 Answer: A

XOR is associative & commutative.
A) True B) False
👉 Answer: A

🧩 LOGICAL REASONING / CODING LOGIC — MCQs
Time complexity of Merge Sort:
A) O(n²) B) O(n log n) C) O(n) D) O(log n)
👉 Answer: B

Maximum edges in undirected graph with n nodes:
A) n² B) n(n-1) C) n(n-1)/2 D) 2n
👉 Answer: C

Space complexity of recursive DFS:
A) O(1) B) O(n²) C) O(n) D) O(log n)
👉 Answer: C

Queue can be implemented using
A) Stack B) Array C) Linked list D) All of the above
👉 Answer: D

BFS uses
A) Stack B) Queue C) Deque D) Heap
👉 Answer: B

💡 GENERAL COMPUTER SCIENCE — MCQs
ASCII uses
A) 7 bits B) 8 bits C) 16 bits D) 32 bits
👉 Answer: A

Primary memory is
A) ROM B) RAM C) Cache D) HDD
👉 Answer: B

Interpreter works
A) Line-by-line B) Whole program C) Machine code only D) None
👉 Answer: A

Which is volatile?
A) SSD B) RAM C) CD-ROM D) Hard Disk
👉 Answer: B

Bluetooth uses
A) WiFi B) Infrared C) RF waves D) Fibre optics
👉 Answer: C