Typical java interview questions sorted by experience


Junior
* Name some of the characteristics of OO programming languages
* What are the access modifiers you know? What does each one do?
* What is the difference between overriding and overloading a method in Java?
* What’s the difference between an Interface and an abstract class?
* Can an Interface extend another Interface?
* What does the static word mean in Java?
* Can a static method be overridden in Java?
* What is Polymorphism? What about Inheritance?
* Can a constructor be inherited?
* Do objects get passed by reference or value in Java? Elaborate on that.
* What’s the difference between using == and .equals on a string?
* What is the hashCode() and equals() used for?
* What does the interface Serializable do? What about Parcelable in Android?
* Why are Array and ArrayList different? When would you use each?
* What’s the difference between an Integer and int?
* What is a ThreadPool? Is it better than using several “simple” threads?
* What the difference between local, instance and class variables?

Mid
* What is reflection?
* What is dependency injection? Can you name a few libraries? (Have you used any?)
* What are strong, soft and weak references in Java?
* What does the keyword synchronized mean?
* Can you have “memory leaks” on Java?
* Do you need to set references to null on Java/Android?
* What does it means to say that a String is immutable?
* What are transient and volatile modifiers?
* What is the finalize() method?
* How does the try{} finally{} works?
* What is the difference between instantiation and initialisation of an object?
* When is a static block run?
* Why are Generics are used in Java?
* Can you mention the design patterns you know? Which of those do you normally use?
* Can you mention some types of testing you know?

Senior
* How does Integer.parseInt() works?
* Do you know what is the “double check locking” problem?
* Do you know the difference between StringBuffer and StringBuilder?
* How is a StringBuilder implemented to avoid the immutable string allocation problem?
* What does Class.forName method do?
* What is Autoboxing and Unboxing?
* What’s the difference between an Enumeration and an Iterator?
* What is the difference between fail-fast and fail safe in Java?
* What is PermGen in Java?
* What is a Java priority queue?
* *s performance influenced by using the same number in different types: Int, Double and Float?
* What is the Java Heap?
* What is daemon thread?
* Can a dead thread be restarted?

Source: medium.

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Java interview questions with answers 👇👇

1. What is Java?
Java is a high-level, object-oriented programming language developed by Sun Microsystems. It is platform-independent, meaning it can run on any device with the Java Virtual Machine (JVM) installed.

2. What is the difference between JDK, JRE, and JVM?
- JDK (Java Development Kit): It is a software development kit used for developing Java applications. It includes the JRE and development tools such as compilers and debuggers.
- JRE (Java Runtime Environment): It is an environment in which Java programs are executed. It includes the JVM and libraries necessary to run Java applications.
- JVM (Java Virtual Machine): It is an abstract machine that provides a runtime environment in which Java bytecode can be executed.

3. What are the main features of Java?
- Object-oriented: Java supports the concept of classes and objects.
- Platform-independent: Java programs can run on any device with a JVM installed.
- Simple: Java has a simple syntax and easy-to-use APIs.
- Secure: Java provides a secure runtime environment with features like bytecode verification and security manager.
- Multithreaded: Java supports multithreading, allowing multiple tasks to run concurrently.

4. What is the difference between an interface and an abstract class in Java?
- Interface: An interface in Java is a collection of abstract methods and constants. A class can implement multiple interfaces but cannot extend multiple classes.
- Abstract class: An abstract class in Java is a class that cannot be instantiated and may contain both abstract and concrete methods. A class can extend only one abstract class.

5. What is the difference between == and equals() method in Java?
- ==: The == operator in Java compares the memory addresses of two objects.
- equals(): The equals() method in Java compares the content of two objects. It is used to compare the values of objects.

6. What is a constructor in Java?
A constructor in Java is a special method that is used to initialize an object. It has the same name as the class and does not have a return type.

7. What is the difference between static and non-static methods in Java?
- Static method: A static method in Java belongs to the class rather than an instance of the class. It can be called using the class name.
- Non-static method: A non-static method in Java belongs to an instance of the class and can only be called using an object of the class.

8. What is the difference between checked and unchecked exceptions in Java?
- Checked exception: Checked exceptions are checked at compile time and must be handled by the programmer using try-catch or throws keyword.
- Unchecked exception: Unchecked exceptions are not checked at compile time and do not need to be handled by the programmer.

9. What is method overloading in Java?
Method overloading in Java is a feature that allows a class to have multiple methods with the same name but different parameters. The compiler determines which method to call based on the number and type of arguments passed.

10. What is method overriding in Java?
Method overriding in Java is a feature that allows a subclass to provide a specific implementation of a method that is already defined in its superclass. The overridden method must have the same name, return type, and parameters as the method in the superclass.

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Python interview questions with answers 👇👇

1. What is Python?
Python is a high-level, interpreted programming language known for its simplicity and readability. It supports multiple programming paradigms, including procedural, object-oriented, and functional programming.

2. What are the key features of Python?
- Easy-to-read syntax
- Dynamic typing
- Interpreted language
- Extensive standard library
- Object-oriented programming support
- Cross-platform compatibility

3. What is the difference between Python 2 and Python 3?
Python 2 and Python 3 are two major versions of the Python programming language. Some key differences include:
- Print statement: In Python 2, print is a statement, while in Python 3, it is a function.
- Unicode support: Python 3 handles strings as Unicode by default, whereas Python 2 uses ASCII strings.
- Integer division: In Python 3, the division of two integers results in a float, whereas in Python 2, it truncates the result to an integer.

4. What are the different data types in Python?
Python supports various data types, including:
- Integers
- Floats
- Strings
- Lists
- Tuples
- Dictionaries
- Sets
- Booleans

5. What is a Python decorator?
A decorator in Python is a design pattern that allows you to modify or extend the behavior of functions or methods without changing their code. Decorators are implemented using the @decorator_name syntax.

6. What is a lambda function in Python?
A lambda function in Python is an anonymous function defined using the lambda keyword. It is used for creating small, one-line functions without a name.

7. What is a list comprehension in Python?
List comprehension is a concise way to create lists in Python by iterating over an iterable and applying an expression to each element. It provides a more readable and efficient way to create lists compared to traditional loops.

8. How can you handle exceptions in Python?
Exceptions in Python can be handled using try-except blocks. The code that may raise an exception is placed inside the try block, and the exception handling logic is written in the except block.

9. What is the difference between deep copy and shallow copy in Python?
- Shallow copy: A shallow copy creates a new object but does not copy the contents of nested objects. Changes made to nested objects in the copy affect the original object.
- Deep copy: A deep copy creates a new object and recursively copies the contents of nested objects. Changes made to nested objects in the copy do not affect the original object.

10. How can you open and read a file in Python?
You can open and read a file in Python using the built-in open() function. Here's an example:

with open('filename.txt', 'r') as file:
    content = file.read()
    print(content)

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Common Programming Interview Questions

How do you reverse a string?
How do you determine if a string is a palindrome?
How do you calculate the number of numerical digits in a string?
How do you find the count for the occurrence of a particular character in a string?
How do you find the non-matching characters in a string?
How do you find out if the two given strings are anagrams?
How do you calculate the number of vowels and consonants in a string?
How do you total all of the matching integer elements in an array?
How do you reverse an array?
How do you find the maximum element in an array?
How do you sort an array of integers in ascending order?
How do you print a Fibonacci sequence using recursion?
How do you calculate the sum of two integers?
How do you find the average of numbers in a list?
How do you check if an integer is even or odd?
How do you find the middle element of a linked list?
How do you remove a loop in a linked list?
How do you merge two sorted linked lists?
How do you implement binary search to find an element in a sorted array?
How do you print a binary tree in vertical order?

Conceptual Coding Interview Questions

What is a data structure?
What is an array?
What is a linked list?
What is the difference between an array and a linked list?
What is LIFO?
What is FIFO?
What is a stack?
What are binary trees?
What are binary search trees?
What is object-oriented programming?
What is the purpose of a loop in programming?
What is a conditional statement?
What is debugging?
What is recursion?
What are the differences between linear and non-linear data structures?


General Coding Interview Questions

What programming languages do you have experience working with?
Describe a time you faced a challenge in a project you were working on and how you overcame it.
Walk me through a project you’re currently or have recently worked on.
Give an example of a project you worked on where you had to learn a new programming language or technology. How did you go about learning it?
How do you ensure your code is readable by other developers?
What are your interests outside of programming?
How do you keep your skills sharp and up to date?
How do you collaborate on projects with non-technical team members?
Tell me about a time when you had to explain a complex technical concept to a non-technical team member.
How do you get started on a new coding project?

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How to revise DSA:

- Look at a question
- 100% confidence If you instantly can remember the way it is solved, skip
- 70%, know the approach, try coding only the important bits and dry run against some cases
- 50%, having some confusion in head, code and run
- <30% treat it as new

Complete DSA Roadmap

|-- Basic_Data_Structures
| |-- Arrays
| |-- Strings
| |-- Linked_Lists
| |-- Stacks
| └─ Queues
|
|-- Advanced_Data_Structures
| |-- Trees
| | |-- Binary_Trees
| | |-- Binary_Search_Trees
| | |-- AVL_Trees
| | └─ B-Trees
| |
| |-- Graphs
| | |-- Graph_Representation
| | | |- Adjacency_Matrix
| | | └ Adjacency_List
| | |
| | |-- Depth-First_Search
| | |-- Breadth-First_Search
| | |-- Shortest_Path_Algorithms
| | | |- Dijkstra's_Algorithm
| | | └ Bellman-Ford_Algorithm
| | |
| | └─ Minimum_Spanning_Tree
| | |- Prim's_Algorithm
| | └ Kruskal's_Algorithm
| |
| |-- Heaps
| | |-- Min_Heap
| | |-- Max_Heap
| | └─ Heap_Sort
| |
| |-- Hash_Tables
| |-- Disjoint_Set_Union
| |-- Trie
| |-- Segment_Tree
| └─ Fenwick_Tree
|
|-- Algorithmic_Paradigms
| |-- Brute_Force
| |-- Divide_and_Conquer
| |-- Greedy_Algorithms
| |-- Dynamic_Programming
| |-- Backtracking
| |-- Sliding_Window_Technique
| |-- Two_Pointer_Technique
| └─ Divide_and_Conquer_Optimization
| |-- Merge_Sort_Tree
| └─ Persistent_Segment_Tree
|
|-- Searching_Algorithms
| |-- Linear_Search
| |-- Binary_Search
| |-- Depth-First_Search
| └─ Breadth-First_Search
|
|-- Sorting_Algorithms
| |-- Bubble_Sort
| |-- Selection_Sort
| |-- Insertion_Sort
| |-- Merge_Sort
| |-- Quick_Sort
| └─ Heap_Sort
|
|-- Graph_Algorithms
| |-- Depth-First_Search
| |-- Breadth-First_Search
| |-- Topological_Sort
| |-- Strongly_Connected_Components
| └─ Articulation_Points_and_Bridges
|
|-- Dynamic_Programming
| |-- Introduction_to_DP
| |-- Fibonacci_Series_using_DP
| |-- Longest_Common_Subsequence
| |-- Longest_Increasing_Subsequence
| |-- Knapsack_Problem
| |-- Matrix_Chain_Multiplication
| └─ Dynamic_Programming_on_Trees
|
|-- Mathematical_and_Bit_Manipulation_Algorithms
| |-- Prime_Numbers_and_Sieve_of_Eratosthenes
| |-- Greatest_Common_Divisor
| |-- Least_Common_Multiple
| |-- Modular_Arithmetic
| └─ Bit_Manipulation_Tricks
|
|-- Advanced_Topics
| |-- Trie-based_Algorithms
| | |-- Auto-completion
| | └─ Spell_Checker
| |
| |-- Suffix_Trees_and_Arrays
| |-- Computational_Geometry
| |-- Number_Theory
| | |-- Euler's_Totient_Function
| | └─ Mobius_Function
| |
| └─ String_Algorithms
| |-- KMP_Algorithm
| └─ Rabin-Karp_Algorithm
|
|-- OnlinePlatforms
| |-- LeetCode
| |-- HackerRank

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Top 10 Python Interview Questions

1. What is Python and what are its key features?
Python is a high-level, interpreted programming language known for its simplicity and readability. Its key features include dynamic typing, automatic memory management, a large standard library, and support for multiple programming paradigms (such as procedural, object-oriented, and functional programming).

2. What are the differences between Python 2 and Python 3?
Python 2 and Python 3 are two major versions of the Python programming language. Some key differences include:
- Python 3 has stricter syntax rules and is not backward compatible with Python 2.
- Python 3 has improved Unicode support and better handling of byte strings.
- Python 3 has some new features and improvements over Python 2, such as the print function being replaced by the print() function.

3. Explain the difference between list and tuple in Python.
- Lists are mutable, meaning their elements can be changed after creation, while tuples are immutable and their elements cannot be changed.
- Lists are defined using square brackets [], while tuples are defined using parentheses ().
- Lists are typically used for collections of items that may need to be modified, while tuples are used for fixed collections of items that should not change.

4. What is PEP 8 and why is it important in Python programming?
PEP 8 is the official style guide for Python code, outlining best practices for writing clean, readable, and maintainable code. Following PEP 8 helps ensure consistency across projects, makes code easier to understand and maintain, and promotes good coding habits within the Python community.

5. How do you handle exceptions in Python?
Exceptions in Python can be handled using try-except blocks. The code that may raise an exception is placed within the try block, and any potential exceptions are caught and handled in the except block. Additionally, you can use the finally block to execute cleanup code regardless of whether an exception occurs.

6. What is a decorator in Python and how do you use it?
A decorator in Python is a function that takes another function as input and extends or modifies its behavior without changing its source code. Decorators are typically used to add functionality to functions or methods, such as logging, authentication, or performance monitoring. To use a decorator, you simply place the "@decorator_name" above the function definition.

7. Explain the difference between '==' and 'is' in Python.
The '==' operator checks for equality of values between two objects, while the 'is' operator checks for identity, meaning it compares whether two objects refer to the same memory location. In other words, '==' checks if two objects have the same value, while 'is' checks if they are the same object.

8. How do you create a virtual environment in Python?
You can create a virtual environment in Python using the venv module, which is included in the standard library. To create a virtual environment, you run the command "python -m venv myenv" in your terminal or command prompt, where "myenv" is the name of your virtual environment. You can then activate the virtual environment using the appropriate command for your operating system.

9. What is the difference between a shallow copy and a deep copy in Python?
A shallow copy creates a new object but does not recursively copy nested objects within it, meaning changes to nested objects will affect both the original and copied objects. A deep copy creates a new object and recursively copies all nested objects within it, ensuring that changes to nested objects do not affect the original object.

10. How do you handle file I/O operations in Python?
File I/O operations in Python can be performed using built-in functions such as open(), read(), write(), close(), and more. To read from a file, you open it in read mode ('r') and use functions like read() or readline(). To write to a file, you open it in write mode ('w') or append mode ('a') and use functions like write() or writelines().

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Top 10 Java Interview Questions & Answers

1. What is Java and what are its key features?
Java is a high-level, object-oriented programming language that is designed to run on any platform. Its key features include platform independence, automatic memory management, strong type checking, and support for multithreading.

2. What is the difference between JDK, JRE, and JVM?
- JDK (Java Development Kit) is a software development kit that includes tools for developing, debugging, and monitoring Java applications.
- JRE (Java Runtime Environment) is a runtime environment that allows you to run Java applications. It includes the JVM (Java Virtual Machine) and necessary libraries.
- JVM (Java Virtual Machine) is an abstract machine that executes Java bytecode. It provides platform independence by running the same bytecode on different platforms.

3. What are the differences between abstract classes and interfaces in Java?
- An abstract class can have both abstract and non-abstract methods, while an interface can only have abstract methods.
- A class can extend only one abstract class, but it can implement multiple interfaces.
- An abstract class can have instance variables, while an interface cannot.
- An abstract class can provide default implementations for some methods, while an interface cannot.

4. What are the access modifiers in Java?
Java has four access modifiers:
- public: accessible from anywhere
- private: accessible only within the same class
- protected: accessible within the same package or subclasses
- default (no modifier): accessible within the same package

5. What is the difference between a class variable and an instance variable in Java?
- A class variable, also known as a static variable, is shared among all instances of a class. It is declared with the static keyword and is accessed using the class name.
- An instance variable is unique to each instance of a class. It is declared without the static keyword and is accessed using the instance name.

6. What is the difference between method overloading and method overriding in Java?
- Method overloading occurs when multiple methods in the same class have the same name but different parameters. The compiler determines which method to call based on the number and types of arguments.
- Method overriding occurs when a subclass provides a different implementation of a method that is already defined in its superclass. The method in the subclass must have the same name, return type, and parameters as the method in the superclass.

7. What is a constructor in Java?
A constructor is a special method that is used to initialize objects of a class. It has the same name as the class and does not have a return type. Constructors are called automatically when an object is created using the new keyword.

8. What are exceptions in Java and how do you handle them?
Exceptions are events that occur during the execution of a program that disrupts the normal flow of instructions. In Java, exceptions are represented by objects. They can be handled using try-catch blocks. The code that may throw an exception is placed within the try block, and any potential exceptions are caught and handled in the catch block.

9. What is multithreading in Java?
Multithreading is a feature of Java that allows multiple threads of execution to run concurrently within a single program. Each thread represents an independent flow of control, allowing for parallel execution of tasks. Multithreading can improve performance by utilizing available CPU resources effectively.

10. What is the difference between ArrayList and LinkedList in Java?
- ArrayList is implemented as a resizable array, while LinkedList is implemented as a doubly linked list.
- ArrayList provides fast random access to elements using indexes, while LinkedList provides fast insertion and deletion at both ends.
- ArrayList uses more memory than LinkedList because it needs to allocate memory for a fixed-size array, while LinkedList only needs to allocate memory for each element and its references.

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Top coding interview questions & answers Part-1 👇👇

1. What is the difference between a stack and a queue?
A stack is a data structure that follows the Last-In-First-Out (LIFO) principle, meaning that the last element added is the first one to be removed. A queue, on the other hand, follows the First-In-First-Out (FIFO) principle, where the first element added is the first one to be removed.

2. Explain the concept of recursion.
Recursion is a programming technique where a function calls itself to solve a problem. It involves breaking down a complex problem into smaller sub-problems until a base case is reached, which allows the function to stop calling itself and start returning values.

3. What is the time complexity of various sorting algorithms?
Some common sorting algorithms and their time complexities are:
- Bubble Sort: O(n^2)
- Insertion Sort: O(n^2)
- Selection Sort: O(n^2)
- Merge Sort: O(n log n)
- Quick Sort: O(n log n)
- Heap Sort: O(n log n)

4. What is the difference between an abstract class and an interface?
An abstract class can have both implemented and unimplemented methods, while an interface can only have unimplemented methods. A class can extend only one abstract class but can implement multiple interfaces.

5. What is the difference between a deep copy and a shallow copy?
A shallow copy creates a new object that references the same memory locations as the original object, while a deep copy creates a new object with its own memory and copies the values from the original object.

6. Explain the concept of polymorphism.
Polymorphism is the ability of an object to take on many forms. It allows objects of different classes to be treated as objects of a common superclass. This enables code to be written that can work with objects of different classes, as long as they share a common interface or superclass.

7. What is the difference between an instance variable and a static variable?
An instance variable belongs to an instance of a class and has separate copies for each instance. A static variable, on the other hand, belongs to the class itself and is shared by all instances of that class.

8. How does garbage collection work in Java?
Garbage collection in Java automatically frees up memory by deallocating objects that are no longer reachable or in use. The Java Virtual Machine (JVM) keeps track of all objects and their references, and periodically identifies and removes objects that are no longer needed.

9. Explain the concept of encapsulation.
Encapsulation is the practice of hiding internal details of an object and providing access to its functionality through well-defined interfaces. It helps in achieving data abstraction, data hiding, and code modularity.

10. What is the difference between a linked list and an array?
An array is a fixed-size data structure that stores elements in contiguous memory locations, allowing for random access using indices. A linked list, on the other hand, is a dynamic data structure where elements are stored in separate nodes that contain references to the next node, allowing for efficient insertion and deletion but slower random access.

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Top coding interview questions & answers Part-2 👇👇

11. What is the difference between an instance method and a static method?
An instance method operates on an instance of a class and can access instance variables and methods. A static method belongs to the class itself and can only access static variables and methods.

12. Explain the concept of inheritance.
Inheritance is a mechanism in object-oriented programming where one class inherits properties and behaviors from another class. The class being inherited from is called the superclass or base class, while the class inheriting is called the subclass or derived class. Inheritance allows for code reuse and promotes code organization.

13. What is the difference between stack memory and heap memory?
Stack memory is used for storing local variables and function calls, while heap memory is used for dynamically allocated memory using keywords like "new" or "malloc". Stack memory is managed by the compiler, while heap memory must be managed manually by the programmer.

14. What is a hashtable and how does it work?
A hash table (or hash map) is a data structure that allows for efficient insertion, deletion, and retrieval of key-value pairs. It uses a hash function to map keys to an index in an array, where values are stored. Collisions can occur when multiple keys map to the same index, which can be resolved using techniques like chaining or open addressing.

15. Explain the concept of deadlock.
Deadlock occurs when two or more processes are unable to proceed because each is waiting for a resource held by another process, resulting in a circular dependency. Deadlocks can be prevented by using techniques like resource allocation graphs, deadlock avoidance algorithms, or by implementing mechanisms like locks or semaphores.

16. What are some advantages of using object-oriented programming?
Advantages of object-oriented programming include code reusability, modularity, encapsulation, easier maintenance and debugging, improved code organization, and increased productivity through abstraction and polymorphism.

17. What is dynamic programming?
Dynamic programming is an algorithmic technique where complex problems are broken down into simpler overlapping subproblems, which are solved once and their solutions are stored for future reference. This technique helps avoid redundant computations and improves efficiency.

18. How does binary search work?
Binary search is an efficient algorithm for finding a target value within a sorted array. It compares the target value with the middle element of the array and narrows down the search space by half with each comparison until the target value is found or determined to be absent.

19. What are some common data structures used in computer science?
Some common data structures include arrays, linked lists, stacks, queues, trees (binary trees, AVL trees, etc.), heaps, hash tables, graphs, and sets.

20. Explain the concept of Big O notation.
Big O notation is used to describe the performance or complexity of an algorithm in terms of its input size. It represents the upper bound or worst-case scenario of an algorithm's time or space complexity. For example, O(1) represents constant time complexity, O(n) represents linear time complexity, O(n^2) represents quadratic time complexity, etc.

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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.)

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Top 10 Javascript Interview Questions With Answers 👇👇

1. What is JavaScript?

JavaScript is a high-level, interpreted programming language that is used to make web pages interactive and dynamic. It is commonly used for front-end development and can also be used for back-end development with the help of Node.js.

2. What are the data types in JavaScript?

JavaScript has six primitive data types: string, number, boolean, null, undefined, and symbol. It also has an object data type, which includes arrays and functions.

3. What is the difference between == and === in JavaScript?

The == operator compares the values of two variables, while the === operator compares both the values and the types of the variables. For example, 5 == "5" would return true, but 5 === "5" would return false.

4. What is a closure in JavaScript?

A closure is a function that has access to its own scope, the outer function's scope, and the global scope. It allows for encapsulation and private data in JavaScript.

5. What is the use of the 'this' keyword in JavaScript?

The 'this' keyword refers to the object that is currently executing the current function. Its value is determined by how a function is called.

6. What are callbacks in JavaScript?

A callback is a function that is passed as an argument to another function and is executed after a specific event or task has been completed. Callbacks are commonly used in asynchronous programming.

7. What are arrow functions in JavaScript?

Arrow functions are a more concise way to write function expressions in JavaScript. They have a shorter syntax and do not bind their own 'this' value.

8. What is event bubbling in JavaScript?

Event bubbling is a mechanism in which an event triggered on a child element will also trigger on its parent elements, propagating up the DOM tree.

9. What is the difference between let and var in JavaScript?

The let keyword was introduced in ES6 and is used to declare block-scoped variables, while var declares function-scoped variables. Variables declared with var are hoisted to the top of their function scope, while let variables are not.

10. How does prototypal inheritance work in JavaScript?

In JavaScript, objects can inherit properties and methods from other objects through prototype chaining. When a property or method is accessed on an object, JavaScript will look up the prototype chain to find it if it's not directly on the object itself.

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100+ Practice Questions

❍ C/C++
❍ Python
❍ JavaScript
❍ Java
❍ C#
❍ Golang

➊ Simple Numbers

➀ Find a digit at a specific place in a number
➁ Find count of digits in a number
➂ Find the largest digit
➃ Find the 2nd largest digit
➄ Find the kth largest digit
➅ Find the smallest digit
➆ Find the 2nd smallest digit
➇ Find the kth smallest digit
➈ Find generic root (sum of all digits) of a number
➉ Reverse the digits in a number
➀➀ Rotate the digits in a number
➀➁ Is the number a palindrome?
➀➂ Find sum of 'n' numbers
➀➃ Check if a number is perfect square
➀➄ Find a number in an AP sequence
➀➅ Find a number in a GP sequence
➀➆ Find a number in fibonacci sequence
➀➇ Check number divisibility by 2, 3, 5, 9
➀➈ Check if a number is primary or not
20. Given a number, print all primes smaller than it
➁➀ Check if a number is circular prime or not
➁➁ Find all prime factors of a number
➁➂ Find the GCD of 2 numbers
➁➃ Find the LCM of 2 numbers
➁➄ Find the factorial of a number
➁➅ Find the exponentiation of a number

➋ Unit Conversion

➀ Number Base (Binary, Octal, Hexadecimal, Decimal)
➁ Weight (gram, kg, pound)
➂ Height (cm, m, inch, feet)
➃ Temperature (centigrade, fahrenhite)
➄ Distance (km, mile)
➅ Area (m², km², acre)
➆ Volume (ltr, gallon)
➇ Time (sec, min, hour)
➈ Currency

➌ Calculator

➀ Loan EMI Calculator
➁ Fixed Deposit Returns Calculator
➂ Interest Calculator
➃ BMI Calculator
➄ Item Price (considering tax, discount, shipping)
➅ Tip Calculator

➍ Geometry

➀ Find distance between 2 points
➁ Given 2 sides of a right angle triangle, find the 3rd
➂ Find 3rd angle of a triangle when 2 are given
➃ Area of a triangle when 3 sides are given
➄ Area of a right angle triangle
➅ Perimeter of a Square
➆ Area of a Square
➇ Perimeter of a Rectangle
➈ Area of a Rectangle
➉ Circumference of a Circle
➀➀ Area of a Circle
➀➁ Circumference of a Semi-Circle
➀➂ Area of a Semi-Circle
➀➃ Area of a Ring
➀➄ Circumference of an Ellipse
➀➅ Area of an Ellipse
➀➆ Suface Area of a Sphere
➀➇ Volume of a Sphere
➀➈ Surface Area of a Hemisphere
20. Volume of a Hemisphere
➁➀ Surface area of a Cube
➁➁ Volume of a Cube
➁➂ Surface area of a Cylinder
➁➃ Volume of a Cylinder

➎ Vector

➀ Find Scalar Multiplication of a vector
➁ Find addition/subtraction of vectors
➂ Find magnitude of a vector
➃ Find an unit vector along a given vector
➄ Find dot product of 2 vectors
➅ Find cross product of 2 vectors
➆ Check if 2 vectors are orthogonal

➏ Matrix

➀ Find the determinant of a matrix
➁ Find Scalar Multiplication of a matrix
➂ Find addition/subtraction of matrices
➃ Find the transpose of a matrix
➄ Find if 2 matrices are orthogonal
➅ Find inverse of a 2x2 and 3x3 matrix

➐ Set

➀ Find Union of 2 sets
➁ Find Intersection of 2 sets
➂ Find the Difference of 2 sets
➃ Find the Symmetric Difference of 2 sets
➄ Find if a set is subset/superset of another set
➅ Find if 2 sets are disjoints

➑ Special Numbers

➀ Strong Number
➁ Perfect Number
➂ Armstrong Number
➃ Harshad Number
➄ Kaprekar Number
➅ Lychrel Number
➆ Narcissistic Decimal Number
➇ Lucus Number
➈ Catalan Number
➉ Duck Number
➀➀ Ugly Number
➀➁ Abundant Number
➀➂ Deficient Number
➀➃ Automorphic Number
➀➄ Magic Number
➀➅ Friendly Pair Numbers
➀➆ Neon Number
➀➇ Spy Number
➀➈ Happy Number
20. Sunny Number
➁➀ Disarium Number
➁➁ Pronic Number
➁➂ Trimorphic Number
➁➃ Evil Number
➁➄ Amicable Pairs

⬘ If you want to excel in programming, practice a lot.

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⬙ Problems based on numbers are easy to start with and they help in improving your analytical skills.

Here are the 50 JavaScript interview questions for 2024

1. What is JavaScript?
2. What are the data types in JavaScript?
3. What is the difference between null and undefined?
4. Explain the concept of hoisting in JavaScript.
5. What is a closure in JavaScript?
6. What is the difference between “==” and “===” operators in JavaScript?
7. Explain the concept of prototypal inheritance in JavaScript.
8. What are the different ways to define a function in JavaScript?
9. How does event delegation work in JavaScript?
10. What is the purpose of the “this” keyword in JavaScript?
11. What are the different ways to create objects in JavaScript?
12. Explain the concept of callback functions in JavaScript.
13. What is event bubbling and event capturing in JavaScript?
14. What is the purpose of the “bind” method in JavaScript?
15. Explain the concept of AJAX in JavaScript.
16. What is the “typeof” operator used for?
17. How does JavaScript handle errors and exceptions?
18. Explain the concept of event-driven programming in JavaScript.
19. What is the purpose of the “async” and “await” keywords in JavaScript?
20. What is the difference between a deep copy and a shallow copy in JavaScript?
21. How does JavaScript handle memory management?
22. Explain the concept of event loop in JavaScript.
23. What is the purpose of the “map” method in JavaScript?
24. What is a promise in JavaScript?
25. How do you handle errors in promises?
26. Explain the concept of currying in JavaScript.
27. What is the purpose of the “reduce” method in JavaScript?
28. What is the difference between “null” and “undefined” in JavaScript?
29. What are the different types of loops in JavaScript?
30. What is the difference between “let,” “const,” and “var” in JavaScript?
31. Explain the concept of event propagation in JavaScript.
32. What are the different ways to manipulate the DOM in JavaScript?
33. What is the purpose of the “localStorage” and “sessionStorage” objects?
34. How do you handle asynchronous operations in JavaScript?
35. What is the purpose of the “forEach” method in JavaScript?
36. What are the differences between “let” and “var” in JavaScript?
37. Explain the concept of memoization in JavaScript.
38. What is the purpose of the “splice” method in JavaScript arrays?
39. What is a generator function in JavaScript?
40. How does JavaScript handle variable scoping?
41. What is the purpose of the “split” method in JavaScript?
42. What is the difference between a deep clone and a shallow clone of an object?
43. Explain the concept of the event delegation pattern.
44. What are the differences between JavaScript’s “null” and “undefined”?
45. What is the purpose of the “arguments” object in JavaScript?
46. What are the different ways to define methods in JavaScript objects?
47. Explain the concept of memoization and its benefits.
48. What is the difference between “slice” and “splice” in JavaScript arrays?
49. What is the purpose of the “apply” and “call” methods in JavaScript?
50. Explain the concept of the event loop in JavaScript and how it handles asynchronous operations.