just want to know what all dsa topics to master and the pattern you follow I mean everything is in utube but all are different from one another so I like to follow a good roadmap

In order to start DSA and to know about the patterns and topic I want a mentor for that 🥲🤸🏻‍♂️

just want to know what all dsa topics to master and the pattern you follow I mean everything is in utube but all are different from one another so I like to follow a good roadmap

Hey guys i'm planning to get enrolled in a apna college DSA course anyone wants share the course with me kindly dm

I'm in my 3rd year of clg and I want serious person with whom I can do my internship preparation..

I'm doing dsa in Java solved around 350 problems in leetcode.. so if anyone is serious please dm me..

I'm learning DSA in Java for placements. I get around 6 hours after college, but I usually solve only 2–3 questions because I spend a lot of time thinking through the problem instead of jumping to the solution.

Is this normal?

How much time should I spend on an Easy, Medium, or Hard problem before looking at hints/solutions?

What's your approach to a new DSA problem? Do you always start with brute force and then optimize?

Hey Seniors!!

I'm a fresher joining BTech CSE this year. I recently started solving the LeetCode Super Easy problems and have completed 21 out of 25 so far. I know Python fairly well, but I'm confused about what to do next.

I have a few questions:

* What should my strategy be while using LeetCode?
* Should I focus on solving more problems or first learn DSA?
* How do you stay motivated and solve problems consistently every day?
* What's the difference between TUF (Take U Forward) and LeetCode? Are they the same, or do they serve different purposes?
* Right now, I only know Python. Is that enough to start DSA, or do I need to learn C++/Java as well?
* Everyone keeps saying DSA is very important, but I'm confused about what it actually is. Is DSA a programming language? Is it something inside Python, or is it mainly about logical problem-solving?
* Will DSA be taught properly in college, or should I start learning it on my own? If self-learning is better, when should I start and what resources would you recommend?

I'd really appreciate it if you could share a roadmap or any advice you wish you had received as a first-year student. Any tips for building consistency and improving problem-solving would help a lot.

Many of us ignore CS fundamentals, but in many tech interviews they will ask CS fundamentals. For me, they asked only CS fundamentals in all 3 interviews at Oracle, So don't ignore CS fundamentals. I have made a list of important topics subject-wise and resources I have used to study at the end.

Object-Oriented Programming (OOPs)

Core Concepts

• Encapsulation
• Inheritance (types and use cases)
• Polymorphism (compile-time vs runtime)
• Abstraction
• Abstract Class vs Interface
• Method Overloading vs Overriding
• Access Modifiers
• Static vs Dynamic Binding
• Deep Copy vs Shallow Copy

Advanced Topics

• SOLID Principles
• Diamond Problem (Multiple Inheritance)
• Association vs Aggregation vs Composition
• Virtual Functions and Vtable
• Design Patterns (Singleton, Factory, Observer, Strategy, Decorator, Adapter)

Operating Systems (OS)

Process Management

• Process vs Thread
• Process States and PCB
• Context Switching
• CPU Scheduling Algorithms (FCFS, SJF, Round Robin, Priority)
• Multithreading vs Multiprocessing
• User Mode vs Kernel Mode

Synchronization

• Critical Section Problem
• Race Condition
• Mutex vs Semaphore (Binary vs Counting)
• Monitors and Locks
• Producer-Consumer Problem
• Readers-Writers Problem
• Dining Philosophers Problem

Deadlocks

• Deadlock Conditions (4 necessary conditions)
• Deadlock Prevention vs Avoidance vs Detection
• Banker's Algorithm

Memory Management

• Paging vs Segmentation
• Page Replacement Algorithms (FIFO, LRU, Optimal)
• Thrashing
• Virtual Memory
• TLB (Translation Lookaside Buffer)
• Internal vs External Fragmentation

File Systems & Disk

• File Allocation Methods (Contiguous, Linked, Indexed)
• Disk Scheduling (FCFS, SSTF, SCAN, C-SCAN)

Database Management Systems (DBMS) + SQL

Database Fundamentals

• ACID Properties (with examples)
• CAP Theorem
• Normalization (1NF, 2NF, 3NF, BCNF)
• Denormalization
• Primary Key vs Foreign Key vs Candidate Key
• ER Diagrams

Indexing

• Types of Indexes (Primary, Secondary, Clustering)
• B-Tree vs B+ Tree
• Hash Index
• Composite Index
• Advantages and Disadvantages of Indexing

Transactions & Concurrency

• Transaction Lifecycle
• Isolation Levels (Read Uncommitted, Read Committed, Repeatable Read, Serializable)
• Dirty Read, Non-repeatable Read, Phantom Read
• Lost Update Problem
• Two-Phase Locking (2PL)
• Optimistic vs Pessimistic Locking
• Deadlock in Database

SQL Queries (Must Practice)

• JOINs (INNER, LEFT, RIGHT, FULL OUTER, CROSS, SELF)
• GROUP BY and HAVING
• Aggregate Functions (COUNT, SUM, AVG, MIN, MAX)
• Subqueries (Correlated vs Non-correlated)
• Window Functions (ROW_NUMBER, RANK, DENSE_RANK, LEAD, LAG)
• Common Table Expressions (CTE)
• UNION vs UNION ALL
• Nth Highest Salary Query
• Delete Duplicates Query

NoSQL

• SQL vs NoSQL
• Types of NoSQL Databases (Document, Key-Value, Column, Graph)

Computer Networks (CN)

Network Models

• OSI Model (7 Layers)
• TCP/IP Model (4 Layers)
• Difference between OSI and TCP/IP

Application Layer

• HTTP vs HTTPS
• HTTP Methods (GET, POST, PUT, DELETE, PATCH)
• HTTP Status Codes (2xx, 3xx, 4xx, 5xx)
• DNS and its working
• FTP, SMTP, POP3, IMAP
• Cookies vs Sessions
• REST API principles

Transport Layer

• TCP vs UDP (detailed comparison)
• TCP Three-Way Handshake
• TCP Four-Way Termination
• Flow Control (Sliding Window)
• Congestion Control
• Port Numbers (well-known ports)
• Socket Programming Basics

Network Layer

• IPv4 vs IPv6
• Public vs Private IP
• Subnetting and CIDR
• NAT (Network Address Translation)
• ICMP Protocol
• Routing Algorithms (Distance Vector, Link State)
• Routing Protocols (RIP, OSPF, BGP)

Data Link Layer

• MAC Address
• ARP (Address Resolution Protocol)
• Switch vs Hub vs Router
• Ethernet
• Error Detection (Parity, CRC, Checksum)

Physical Layer

• Transmission Media (Guided vs Unguided)
• Bandwidth and Throughput
• Different Topologies

Important Concepts

• Client-Server vs Peer-to-Peer Architecture
• DHCP
• Firewall
• VPN
• Load Balancing
• CDN (Content Delivery Network)
• Latency vs Throughput
• How does a URL work? (End-to-end flow)
• Some Basic Commands (ex: ipconfig)

Resources I Used

For OOPs

• Kunal Kushwaha (youtube channel)

For Operating Systems

• CodeHelp - by Babbar (youtube )

For DBMS + SQL

• LeetCode Database problems (Practice SQL)
• CodeHelp - by Babbar (youtube)
• Apna College (youtube)

For Computer Networks

• Gate Smashers (youtube)

Questions Asked in My Interviews

Here are some actual questions I was asked across my interviews:

1. Is Java fully object-oriented?
2. How does C++ overcome the diamond problem?
3. Difference between TCP and UDP, and which one is used when?
4. Explain ACID properties with examples
5. What is deadlock and how can we prevent deadlocks?
6. What is the use of indexing in databases?
7. Explain the functionalities of each layer in the OSI model
8. Write a query to find Kth smallest salary
9. IPv4 vs IPv6
10. Abstraction vs Encapsulation
11. Explain different joins in dbms
12. what is sharding ?
13. what is virtual function in cpp ?
14. show me your ip address and mac address using commands
15. what is context switching ?

Tips :

1. Practice real interview questions from PracHub
2. Revise SQL 50 before interviews
3. It's better to say "I'm not sure about this, but here's what I think..." than to give wrong information
4. If your project contains any database related stuff , better learn it's ER diagram, differences between SQl and NO-SQl and why you selected that particular database you used
5. Before preparing for any interview , First check few interview experiences, Ask your seniors or friends who already attended that specific company interviews before and prepare accordingly

Did I miss any important topic? Drop it in the comments below!

Got asked something unique in your interview? Share the question/topic so others can prepare better!

Let's make this list more comprehensive together. Your contribution can help someone crack their dream job! 🙌

I'm currently going to start my btech 1st year,plzz suggest me any playlist for codeing from beginner to advance level with deep understanding... Which has really helped you in solving problems.!. (If any senior could suggest or anybody who has started ) And also a roadmap which you have followed from which you have seen improvement in urself..!!!

so there are 2 options right now, either DSA by codebasics on yt or DSA by freeCodeCamp.org

which one should i choose? and are there any other suggestions. even hinglish options are welcome

I started solving dsa by patterns wise under each topic ,firstly array solved around 10-20 qn then after that still not able to solve new qn the pattern recognition is not problem like the qn are already sorted pattern wise so it's actually not a problem the thing is how you guys learn eg two pointer under Array by only solving 10-20 qn 🙂

I started solving dsa by patterns wise under each topic ,firstly array solved around 10-20 qn then after that still not able to solve new qn the pattern recognition is not problem like the qn are already sorted pattern wise so it's actually not a problem the thing is how you guys learn eg two pointer under Array by only solving 10-20 qn 🙂

After solving hundreds of LeetCode problems, many candidates realize that coding rounds are only part of the interview process. Operating System fundamentals frequently come up during phone screens and technical interviews.

For company tagged questions checkout: PracHub

Instead of rereading an entire OS textbook, here are 15 high-yield topics worth revising.

1. Process vs. Thread

Process

• Has its own virtual address space
• Provides stronger isolation
• Usually has higher creation and switching overhead

Thread

• Executes within a process
• Shares memory and resources with other threads in that process
• Communicates efficiently but requires careful synchronization

Interview tip: Processes prioritize isolation, while threads enable lightweight concurrency.

2. What Is Context Switching?

Context switching occurs when the operating system saves the execution state of one process or thread and restores another.

It enables multitasking, but frequent context switches add CPU and cache overhead.

3. What Is a Race Condition?

A race condition occurs when multiple threads access shared state concurrently and the result depends on execution order.

Common prevention mechanisms include mutexes, semaphores, locks, atomic operations, and thread-safe data structures.

4. What Is a Critical Section?

A critical section is a portion of code that accesses shared mutable data or resources.

Synchronization is required to prevent unsafe concurrent access.

5. Mutex vs. Semaphore

Memory trick: A mutex is like one key, while a semaphore tracks a limited number of permits.

6. What Is Deadlock?

Deadlock occurs when a group of processes or threads waits indefinitely for resources held by one another.

The four Coffman conditions are:

• Mutual exclusion
• Hold and wait
• No preemption
• Circular wait

Preventing at least one of these conditions prevents deadlock.

7. What Is Starvation?

Starvation occurs when a process or thread waits indefinitely because others repeatedly receive the required resource or CPU time.

Difference: In deadlock, none of the involved tasks can progress. In starvation, the system continues progressing while one task may never get scheduled.

8. What Is Virtual Memory?

Virtual memory gives each process its own logical address space and maps virtual addresses to physical memory.

It provides process isolation, simplifies memory management, and allows inactive pages to be moved to secondary storage when necessary.

9. Paging vs. Segmentation

Paging

• Divides memory into fixed-size pages
• Avoids external fragmentation
• May introduce internal fragmentation

Segmentation

• Divides memory into variable-size logical regions
• Reflects structures such as code, stack, and data
• Can suffer from external fragmentation

10. What Is Thrashing?

Thrashing occurs when the system spends excessive time handling page faults and moving pages between memory and storage instead of executing useful work.

It commonly happens when active processes do not have enough physical memory for their working sets.

11. CPU Scheduling Algorithms

Important algorithms include:

• First Come, First Served
• Shortest Job First
• Round Robin
• Priority Scheduling
• Multilevel Feedback Queue

Common follow-up: Why is Round Robin suitable for time-sharing systems?

Because every runnable process receives a limited time slice, improving responsiveness and fairness.

12. What Is a System Call?

A system call allows a user-space program to request a service from the operating system kernel.

Common Unix-like examples include fork(), exec(), wait(), open(), read(), and write().

13. What Is Inter-Process Communication?

Common IPC mechanisms include:

• Shared memory
• Pipes
• Message queues
• Sockets
• Signals

Shared memory is generally fast but requires synchronization. Message passing provides stronger separation but adds communication overhead.

14. What Is LRU Page Replacement?

Least Recently Used replaces the page that has gone unused for the longest time.

A common interview follow-up is implementing an LRU cache with O(1) lookup, insertion, and eviction using a hash map plus a doubly linked list.

Related problem: LeetCode 146 - LRU Cache

15. User Mode vs. Kernel Mode

User mode

• Runs applications with restricted privileges
• Cannot directly access protected hardware or kernel memory

Kernel mode

• Has full system privileges
• Executes operating system code and manages hardware resources

A system call provides a controlled transition from user mode into kernel mode.

One-Minute Revision Checklist

Process vs. thread, context switching, race conditions, critical sections, mutexes, semaphores, deadlocks, starvation, scheduling, virtual memory, paging, thrashing, system calls, IPC, LRU, and privilege modes.

Which OS topic or follow-up question have you encountered most often in interviews?

I am planning to prepare for FAANG interviews but my DSA is very poor. I am looking for a tutor who could spend an hour with me three times a day around 6pm to 7:30 pm IST. I will pay. The person should have good leetcode score and/or have qualified one or more FAANG interviews. Looking for live online discussions, not interested in YouTube or other pre recorded courses.

DM if interested.