Coding Interview Resources
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This channel contains the free resources and solution of coding problems which are usually asked in the interviews.

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Here is a great JavaScript interview question!

What the heck is a Promise doing under the hood?

In JavaScript, things usually happen one after the other. It's like a checklist each item gets done before moving to the next.

When a function returns a Promise, it's like making a promise to do something, like fetch data from the internet. But JavaScript doesn't wait around for the data to come back. Instead, it moves on to the next task.

Now, here's where things get interesting. While JavaScript is busy doing other stuff, like running more code, the Promise is off fetching data in the background.

Once the data is fetched, the Promise is fulfilled, and it has some information to share. But JavaScript needs to know when it's time to handle that information. That's where the onFulfilled part of the Promise comes in.

When the Promise is fulfilled, JavaScript takes the onFulfilled code and puts it in a special queue, ready to be run.

Now, async/await enters the scene. When we mark a function as async, we're telling JavaScript, "Hey, this function might take some time to finish, so don't wait up for it."

And when we use the await keyword inside an async function, it's like saying, "Hold on a sec, JavaScript. I need to wait for something important before moving on."

So, when JavaScript encounters an await keyword, it pauses and lets the async function do its thing. If that thing happens to be a Promise, JavaScript knows it can move on to other tasks while waiting for the Promise to resolve.

Once the Promise is resolved, JavaScript picks up where it left off and continues running the code.

Promises and async/await allow JavaScript to handle asynchronous tasks while keeping things organized and in order. Promises handle the background tasks, while async/await makes it easier to work with them in our code, ensuring everything happens in the right sequence.

Web Development Best Resources: https://topmate.io/coding/930165

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15+ Must Watch Movies for ProgrammersπŸ§‘β€πŸ’»πŸ€–

1. The Matrix
2. The Social Network
3. Source Code
4. The Imitation Game
5. Silicon Valley
6. Mr. Robot
7. Jobs
8. The Founder
9. The Social Dilemma
10. The Great Hack
11. Halt and Catch Fire
12. Wargames
13. Hackers
14. Snowden
15. Who Am I

Happy Coding β™₯️
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10 Chrome Extensions Every Developer Should Use

βœ… JSON Viewer – Beautify and view JSON data instantly
βœ… Wappalyzer – Identify the tech stack of any website
βœ… Web Developer – Adds powerful dev tools to your browser
βœ… ColorZilla – Pick and copy any color from a webpage
βœ… React Developer Tools – Debug and inspect React components
βœ… Dark Reader – Enable dark mode on every site
βœ… Session Buddy – Manage tabs and sessions like a pro
βœ… WhatFont – Instantly identify fonts on websites
βœ… Lighthouse – Audit performance, SEO, and accessibility
βœ… AI Prompt Genius – Manage and save prompts for AI tools

React with your favorite emoji if you found a gem in here!
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PREPARING FOR AN ONLINE INTERVIEW?

10 basic tips to consider when invited/preparing for an online interview:

1. Get to know the online technology that the interviewer(s) will use. Is it a phone call, WhatsApp, Skype or Zoom interview? If not clear, ask.

2. Familiarize yourself with the online tools that you’ll be using. Understand how Zoom/Skype works and test it well in advance. Test the sound and video quality.

3. Ensure that your internet connection is stable. If using mobile data, make sure it’s adequate to sustain the call to the end.

4. Ensure the lighting and the background is good. Remove background clutter. Isolate yourself in a place where you’ll not have any noise distractions.

5. For Zoom/Skype calls, use your desktop or laptop instead of your phone. They’re more stable especially for video calls.

6. Mute all notifications on your computer/phone to avoid unnecessary distractions.

7. Ensure that your posture is right. Just because it’s a remote interview does not mean you slouch on your couch. Maintain an upright posture.

8. Prepare on the other job specifics just like you would for a face-to-face interview

9. Dress up like you would for a face-to-face interview.

10. Be all set at least 10 minutes to the start of interview.
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10 Chrome Extensions Every Developer Should Use

βœ… JSON Viewer – Beautify and view JSON data instantly
βœ… Wappalyzer – Identify the tech stack of any website
βœ… Web Developer – Adds powerful dev tools to your browser
βœ… ColorZilla – Pick and copy any color from a webpage
βœ… React Developer Tools – Debug and inspect React components
βœ… Dark Reader – Enable dark mode on every site
βœ… Session Buddy – Manage tabs and sessions like a pro
βœ… WhatFont – Instantly identify fonts on websites
βœ… Lighthouse – Audit performance, SEO, and accessibility
βœ… AI Prompt Genius – Manage and save prompts for AI tools

React with your favorite emoji if you found a gem in here!
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⌨️ Grammar Correction using Python
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Theoretical Questions for Interviews on Array

1. What is an array?

An array is a data structure consisting of a collection of elements, each identified by at least one array index or key.

2. How do you declare an Array?

Each language has its own way of declaring arrays, but the general idea is similar: defining the type of elements and the number of elements or initializing it directly.

βœ… C/C++: int arr[5]; (Declares an array of 5 integers).
βœ… Java: int[] arr = new int[5]; (Declares and initializes an array of 5 integers).
βœ… Python: arr = [1, 2, 3, 4, 5] (Uses a list, which functions like an array and doesn’t require a fixed size).
βœ… JavaScript: let arr = [1, 2, 3, 4, 5]; (Uses arrays without needing a size specification).
βœ… C#: int[] arr = new int[5]; (Declares an array of 5 integers).

3. Can an array be resized at runtime?

An array is fixed in size once created. However, in C, you can resize an array at runtime using Dynamic Memory Allocation (DMA) with malloc() or realloc(). Most modern languages have dynamic-sized arrays like vector in C++, list in Python, and ArrayList in Java, which automatically resize.

4. Is it possible to declare an array without specifying its size?

In C/C++, declaring an array without specifying its size is not allowed and causes a compile-time error. However, in C, we can create a pointer and allocate memory dynamically using malloc(). In C++, we can use vectors where we can declare first and then dynamically add elements. In modern languages like Java, Python, and JavaScript, we can declare without specifying the size.

5. What is the time complexity for accessing an element in an array?

The time complexity for accessing an element in an array is O(1), as it can be accessed directly using its index.

6. What is the difference between an array and a linked list?

An array is a static data structure, while a linked list is a dynamic data structure. Raw arrays have a fixed size, and elements are stored consecutively in memory, while linked lists can grow dynamically and do not require contiguous memory allocation. Dynamic-sized arrays allow flexible size, but the worst-case time complexity for insertion/deletion at the end becomes more than O(1). With a linked list, we get O(1) worst-case time complexity for insertion and deletion.

7. How would you find out the smallest and largest element in an array?

The best approach is iterative (linear search), while other approaches include recursive and sorting.

Iterative method

Algorithm:

1. Initialize two variables:

small = arr[0] (first element as the smallest).

large = arr[0] (first element as the largest).



2. Traverse through the array from index 1 to n-1.


3. If arr[i] > large, update large = arr[i].


4. If arr[i] < small, update small = arr[i].


5. Print the values of small and large.



C++ Code Implementation

#include <iostream>
using namespace std;

void findMinMax(int arr[], int n) {
int small = arr[0], large = arr[0];

for (int i = 1; i < n; i++) {
if (arr[i] > large)
large = arr[i];
if (arr[i] < small)
small = arr[i];
}

cout << "Smallest element: " << small << endl;
cout << "Largest element: " << large << endl;
}

int main() {
int arr[] = {7, 2, 9, 4, 1, 5};
int n = sizeof(arr) / sizeof(arr[0]);

findMinMax(arr, n);

return 0;
}

8. What is the time complexity to search in an unsorted and sorted array?

βœ… Unsorted Array: The time complexity for searching an element in an unsorted array is O(n), as we may need to check every element.
βœ… Sorted Array: The time complexity for searching an element in a sorted array is O(log n) using binary search.

πŸ”Ή O(log n) takes less time than O(n), whereas O(n log n) takes more time than O(n).

Free Coding Interview Resources: https://whatsapp.com/channel/0029VammZijATRSlLxywEC3X
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18 Most common used Java List methods

1. add(E element) - Adds the specified element to the end of the list.
2. addAll(Collection<? extends E> c) - Adds all elements of the specified collection to the end of the list.
3. remove(Object o) - Removes the first occurrence of the specified element from the list.
4. remove(int index) - Removes the element at the specified position in the list.
5. get(int index) - Returns the element at the specified position in the list.
6. set(int index, E element) - Replaces the element at the specified position in the list with the specified element.
7. indexOf(Object o) - Returns the index of the first occurrence of the specified element in the list.
8. contains(Object o) - Returns true if the list contains the specified element.
9. size() - Returns the number of elements in the list.
10. isEmpty() - Returns true if the list contains no elements.
11. clear() - Removes all elements from the list.
12. toArray() - Returns an array containing all the elements in the list.
13. subList(int fromIndex, int toIndex) - Returns a view of the portion of the list between the specified fromIndex, inclusive, and toIndex, exclusive.
14. addAll(int index, Collection<? extends E> c) - Inserts all elements of the specified collection into the list, starting at the specified position.
15. iterator() - Returns an iterator over the elements in the list.
16. sort(Comparator<? super E> c) - Sorts the elements of the list according to the specified comparator.
17. replaceAll(UnaryOperator<E> operator) - Replaces each element of the list with the result of applying the given operator.
18. forEach(Consumer<? super E> action) - Performs the given action for each element of the list until all elements have been processed or the action throws an exception.
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Technical Questions Wipro may ask on their interviews

1. Data Structures and Algorithms:
   - "Can you explain the difference between an array and a linked list? When would you use one over the other in a real-world application?"
   - "Write code to implement a binary search algorithm."

2. Programming Languages:
   - "What is the difference between Java and C++? Can you provide an example of a situation where you would prefer one language over the other?"
   - "Write a program in your preferred programming language to reverse a string."

3. Database and SQL:
   - "Explain the ACID properties in the context of database transactions."
   - "Write an SQL query to retrieve all records from a 'customers' table where the 'country' column is 'India'."

4. Networking:
   - "What is the difference between TCP and UDP? When would you choose one over the other for a specific application?"
   - "Explain the concept of DNS (Domain Name System) and how it works."

5. System Design:
   - "Design a simple online messaging system. What components would you include, and how would they interact?"
   - "How would you ensure the scalability and fault tolerance of a web service or application?"
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30 commonly asked questions in database management system (DBMS) interviews
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1. What is a DBMS?
2. Differentiate between DBMS and RDBMS.
3. What are the advantages and disadvantages of using a DBMS?
4. Explain the three levels of data abstraction in DBMS.
5. What is a database schema?
6. Define normalization and its importance in database design.
7. What are the different types of database models?
8. What is ACID (Atomicity, Consistency, Isolation, Durability) in DBMS?
9. What is a primary key, and why is it important?
10. Explain the concept of foreign keys.
11. Differentiate between a candidate key, primary key, and super key.
12. What is a transaction in a database?
13. Describe the differences between DELETE, TRUNCATE, and DROP commands.
14. What is a view in a database?
15. Explain indexing in databases.
16. What is a stored procedure?
17. What are the advantages of using stored procedures?
18. Describe the differences between clustered and non-clustered indexes.
19. What is a deadlock in DBMS?
20. How can you avoid deadlocks in a database?
21. What is data redundancy, and how can it be minimized?
22. What is a trigger in a database?
23. Describe the different types of joins in SQL.
24. What is a constraint in a database?
25. Explain the differences between a unique key and a primary key.
26. How does SQL differ from NoSQL databases?
27. What is the CAP theorem, and how does it relate to databases?
28. Explain the concept of data warehousing.
29. What are OLTP and OLAP, and how do they differ?
30. How would you approach database performance tuning and optimization?
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Here is a great JavaScript interview question!

What the heck is a Promise doing under the hood?

In JavaScript, things usually happen one after the other. It's like a checklist each item gets done before moving to the next.

When a function returns a Promise, it's like making a promise to do something, like fetch data from the internet. But JavaScript doesn't wait around for the data to come back. Instead, it moves on to the next task.

Now, here's where things get interesting. While JavaScript is busy doing other stuff, like running more code, the Promise is off fetching data in the background.

Once the data is fetched, the Promise is fulfilled, and it has some information to share. But JavaScript needs to know when it's time to handle that information. That's where the onFulfilled part of the Promise comes in.

When the Promise is fulfilled, JavaScript takes the onFulfilled code and puts it in a special queue, ready to be run.

Now, async/await enters the scene. When we mark a function as async, we're telling JavaScript, "Hey, this function might take some time to finish, so don't wait up for it."

And when we use the await keyword inside an async function, it's like saying, "Hold on a sec, JavaScript. I need to wait for something important before moving on."

So, when JavaScript encounters an await keyword, it pauses and lets the async function do its thing. If that thing happens to be a Promise, JavaScript knows it can move on to other tasks while waiting for the Promise to resolve.

Once the Promise is resolved, JavaScript picks up where it left off and continues running the code.

Promises and async/await allow JavaScript to handle asynchronous tasks while keeping things organized and in order. Promises handle the background tasks, while async/await makes it easier to work with them in our code, ensuring everything happens in the right sequence.

Web Development Best Resources: https://topmate.io/coding/930165

ENJOY LEARNING πŸ‘πŸ‘
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Which programming language should I use on interview?

Companies usually let you choose, in which case you should use your most comfortable language. If you know a bunch of languages, prefer one that lets you express more with fewer characters and fewer lines of code, like Python or Ruby. It keeps your whiteboard cleaner.

Try to stick with the same language for the whole interview, but sometimes you might want to switch languages for a question. E.g., processing a file line by line will be far easier in Python than in C++.

Sometimes, though, your interviewer will do this thing where they have a pet question that’s, for example, C-specific. If you list C on your resume, they’ll ask it.

So keep that in mind! If you’re not confident with a language, make that clear on your resume. Put your less-strong languages under a header like β€˜Working Knowledge.’
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Complete roadmap to learn Python and Data Structures & Algorithms (DSA) in 2 months

### Week 1: Introduction to Python

Day 1-2: Basics of Python
- Python setup (installation and IDE setup)
- Basic syntax, variables, and data types
- Operators and expressions

Day 3-4: Control Structures
- Conditional statements (if, elif, else)
- Loops (for, while)

Day 5-6: Functions and Modules
- Function definitions, parameters, and return values
- Built-in functions and importing modules

Day 7: Practice Day
- Solve basic problems on platforms like HackerRank or LeetCode

### Week 2: Advanced Python Concepts

Day 8-9: Data Structures in Python
- Lists, tuples, sets, and dictionaries
- List comprehensions and generator expressions

Day 10-11: Strings and File I/O
- String manipulation and methods
- Reading from and writing to files

Day 12-13: Object-Oriented Programming (OOP)
- Classes and objects
- Inheritance, polymorphism, encapsulation

Day 14: Practice Day
- Solve intermediate problems on coding platforms

### Week 3: Introduction to Data Structures

Day 15-16: Arrays and Linked Lists
- Understanding arrays and their operations
- Singly and doubly linked lists

Day 17-18: Stacks and Queues
- Implementation and applications of stacks
- Implementation and applications of queues

Day 19-20: Recursion
- Basics of recursion and solving problems using recursion
- Recursive vs iterative solutions

Day 21: Practice Day
- Solve problems related to arrays, linked lists, stacks, and queues

### Week 4: Fundamental Algorithms

Day 22-23: Sorting Algorithms
- Bubble sort, selection sort, insertion sort
- Merge sort and quicksort

Day 24-25: Searching Algorithms
- Linear search and binary search
- Applications and complexity analysis

Day 26-27: Hashing
- Hash tables and hash functions
- Collision resolution techniques

Day 28: Practice Day
- Solve problems on sorting, searching, and hashing

### Week 5: Advanced Data Structures

Day 29-30: Trees
- Binary trees, binary search trees (BST)
- Tree traversals (in-order, pre-order, post-order)

Day 31-32: Heaps and Priority Queues
- Understanding heaps (min-heap, max-heap)
- Implementing priority queues using heaps

Day 33-34: Graphs
- Representation of graphs (adjacency matrix, adjacency list)
- Depth-first search (DFS) and breadth-first search (BFS)

Day 35: Practice Day
- Solve problems on trees, heaps, and graphs

### Week 6: Advanced Algorithms

Day 36-37: Dynamic Programming
- Introduction to dynamic programming
- Solving common DP problems (e.g., Fibonacci, knapsack)

Day 38-39: Greedy Algorithms
- Understanding greedy strategy
- Solving problems using greedy algorithms

Day 40-41: Graph Algorithms
- Dijkstra’s algorithm for shortest path
- Kruskal’s and Prim’s algorithms for minimum spanning tree

Day 42: Practice Day
- Solve problems on dynamic programming, greedy algorithms, and advanced graph algorithms

### Week 7: Problem Solving and Optimization

Day 43-44: Problem-Solving Techniques
- Backtracking, bit manipulation, and combinatorial problems

Day 45-46: Practice Competitive Programming
- Participate in contests on platforms like Codeforces or CodeChef

Day 47-48: Mock Interviews and Coding Challenges
- Simulate technical interviews
- Focus on time management and optimization

Day 49: Review and Revise
- Go through notes and previously solved problems
- Identify weak areas and work on them

### Week 8: Final Stretch and Project

Day 50-52: Build a Project
- Use your knowledge to build a substantial project in Python involving DSA concepts

Day 53-54: Code Review and Testing
- Refactor your project code
- Write tests for your project

Day 55-56: Final Practice
- Solve problems from previous contests or new challenging problems

Day 57-58: Documentation and Presentation
- Document your project and prepare a presentation or a detailed report

Day 59-60: Reflection and Future Plan
- Reflect on what you've learned
- Plan your next steps (advanced topics, more projects, etc.)

Best DSA RESOURCES: https://topmate.io/coding/886874

Credits: https://t.me/free4unow_backup

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7 Most Popular Programming Languages in 2025

1. Python

The Jack of All Trades

Why it's loved: Simple syntax, huge community, beginner-friendly.

Used for: Data Science, Machine Learning, Web Development, Automation.

Who uses it: Data analysts, backend developers, researchers, even kids learning to code.


2. JavaScript

The Language of the Web

Why it's everywhere: Runs in every browser, now also on servers (Node.js).

Used for: Frontend & backend web apps, interactive UI, full-stack apps.

Who uses it: Web developers, app developers, UI/UX enthusiasts.


3. Java

The Enterprise Backbone

Why it stands strong: Portable, secure, scalable β€” runs on everything from desktops to Android devices.

Used for: Android apps, enterprise software, backend systems.

Who uses it: Large corporations, Android developers, system architects.


4. C/C++

The Power Players

Why they matter: Super fast, close to the hardware, great for performance-critical apps.

Used for: Game engines, operating systems, embedded systems.

Who uses it: System programmers, game developers, performance-focused engineers.


5. C#

Microsoft’s Darling

Why it's growing: Built into the .NET ecosystem, great for Windows apps and games.

Used for: Desktop applications, Unity game development, enterprise tools.

Who uses it: Game developers, enterprise app developers, Windows lovers.


6. SQL

The Language of Data

Why it’s essential: Every application needs a database β€” SQL helps you talk to it.

Used for: Querying databases, reporting, analytics.

Who uses it: Data analysts, backend devs, business intelligence professionals.


7. Go (Golang)

The Modern Minimalist

Why it’s rising: Simple, fast, and built for scale β€” ideal for cloud-native apps.

Used for: Web servers, microservices, distributed systems.

Who uses it: Backend engineers, DevOps, cloud developers.

Free Coding Resources: https://whatsapp.com/channel/0029VahiFZQ4o7qN54LTzB17
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Java coding interview questions

1. Reverse a String:
Write a Java program to reverse a given string.
2. Find the Largest Element in an Array:
Find and print the largest element in an array.
3. Check for Palindrome:
Determine if a given string is a palindrome (reads the same backward as forward).
4. Factorial Calculation:
Write a function to calculate the factorial of a number.
5. Fibonacci Series:
Generate the first n numbers in the Fibonacci sequence.
6. Check for Prime Number:
Write a program to check if a given number is prime.
7. String Anagrams:
Determine if two strings are anagrams of each other.

8. Array Sorting:
Implement sorting algorithms like bubble sort, merge sort, or quicksort.

9. Binary Search:
Implement a binary search algorithm to find an element in a sorted array.

10. Duplicate Elements in an Array:
Find and print duplicate elements in an array.

11. Linked List Reversal:
Reverse a singly-linked list.

12. Matrix Operations:
Perform matrix operations like addition, multiplication, or transpose.

13. Implement a Stack:
Create a stack data structure and implement basic operations (push, pop).

14. Implement a Queue:
Create a queue data structure and implement basic operations (enqueue, dequeue).

15. Inheritance and Polymorphism:
Implement a class hierarchy with inheritance and demonstrate polymorphism.

16. Exception Handling:
Write code that demonstrates the use of try-catch blocks to handle exceptions.
17. File I/O:
Read from and write to a file using Java's file I/O capabilities.
18. Multithreading:
Create a simple multithreaded program and demonstrate thread synchronization.
19. Lambda Expressions:
Use lambda expressions to implement functional interfaces.
20. Recursive Algorithms:
Solve a problem using recursion, such as computing the factorial or Fibonacci sequence.

Best Java Resources: https://whatsapp.com/channel/0029VamdH5mHAdNMHMSBwg1s

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