100+ Software Engineer Trainee Interview Questions and Answers for Freshers

Check if a given singly linked list of integers is a palindrome or not.

• Traverse the linked list to find the middle element using slow and fast pointers.

• Reverse the second half of the linked list.

• Compare the first half with the reversed second half to determine if it is a palindrome.

• Example: Input: 1 -> 2 -> 3 -> 2 -> 1 -> NULL, Output: true

Implement a function to search for a target integer in a 2D matrix with sorted rows.

• Iterate through each row of the matrix and perform a binary search on each row to find the target integer.

• Start the binary search by considering the entire row as a sorted array.

• If the target is found in any row, return 'TRUE'; otherwise, return 'FALSE'.

Calculate total score based on guessing colors in a slot machine.

• Iterate through each slot in the original and guess strings to compare colors.

• Count perfect hits when color matches in correct slot, and pseudo-hits when color matches in different slot.

• Calculate total score by adding perfect hits and pseudo-hits.

• Handle edge cases like invalid input strings or exceeding constraints.

Find the maximum level sum in a binary tree by calculating the sum of nodes at each level.

• Traverse the binary tree level by level and calculate the sum of nodes at each level.

• Keep track of the maximum level sum encountered so far.

• Return the maximum level sum as the final result.

Calculate x raised to the power of n. Handle edge case of 0^0 = 1.

• Accept x and n as input from user

• Compute x^n and display the result

• Handle edge case of 0^0 = 1

• Ensure x is between 0 and 8, n is between 0 and 9

Check if a given singly linked list is a palindrome or not.

• Traverse the linked list to find the middle element using slow and fast pointers.

• Reverse the second half of the linked list.

• Compare the first half with the reversed second half to determine if it's a palindrome.

Rotate an array left by a specified number of elements for each query.

• Parse input: read number of test cases, array size, queries, and array elements

• For each query, left rotate the array by the specified number of elements

• Return the modified array for each query

Given an array and a target sum, find pairs of elements that add up to the target sum.

• Iterate through the array and for each element, check if the complement (target sum - current element) exists in a hash set.

• If the complement exists, add the pair to the result list.

• Sort the result list based on the first element of each pair, and then the second element if the first elements are equal.

The N Queens Problem involves finding all possible placements of N queens on an N x N chessboard where no two queens threaten each other.

• Understand the constraints of the problem: N represents the size of the chessboard and the number of queens, and queens can attack each other if they are in the same row, column, or diagonal.

• Implement a backtracking algorithm to explore all possible configurations of queen placements without conflicts.

• Ensure that each valid configuration is ...read more

The question covers topics like two's complement, data structures, machine learning, and OOPs concepts in Java.

• Two's complement of a number 1001 is -0111.

• Data structures are ways of organizing and storing data in a computer so that it can be accessed and used efficiently. Examples include arrays, linked lists, stacks, queues, trees, and graphs.

• Machine learning is a subset of artificial intelligence that involves training algorithms to make predictions or decisions based on da...read more

Develop a 'To Do List' application with modern design and functionality like 'Add', 'Edit', 'Delete', and 'View List' within ½ hour.

• Use HTML, CSS, and JavaScript for front-end development

• Implement CRUD operations for tasks (Create, Read, Update, Delete)

• Design a user-friendly interface with header and footer

• Utilize localStorage or backend server for data storage

Hooks are functions that allow us to use state and other React features in functional components.

• useState is a hook that allows us to add state to functional components.

• useRef is a hook that allows us to create a mutable reference that persists across renders.

• useEffect is a hook that allows us to perform side effects in functional components.

• useState example: const [count, setCount] = useState(0);

• useRef example: const inputRef = useRef(null);

• useEffect example: useEffect(() =>...read more

Overloading is having multiple methods in the same class with the same name but different parameters. Overriding is implementing a method in a subclass that is already present in the superclass.

• Overloading involves multiple methods with the same name but different parameters

• Overriding involves implementing a method in a subclass that is already present in the superclass

• Overloading is determined at compile time, while overriding is determined at runtime

I am familiar with JDBC, Servlets, Hibernate, Spring, Apache Tomcat, and build tools like Maven.

• Experience with JDBC for database connectivity in Java applications

• Knowledge of Servlets for handling web requests and responses

• Understanding of Hibernate for object-relational mapping in Java

• Familiarity with Spring framework for building enterprise Java applications

• Experience with Apache Tomcat for deploying Java web applications

• Proficiency in build tools like Maven for project ma...read more

Waterfall model is a linear sequential approach, while incremental model divides the project into small increments.

• Waterfall model follows a linear and sequential approach, where each phase must be completed before moving on to the next.

• Incremental model divides the project into small increments, with each increment building upon the previous one.

• Waterfall model is less flexible to changes, as requirements are finalized early in the process.

• Incremental model allows for change...read more

Finding the maximum length of palindromic substring from an array of strings using Typescript.

• Iterate through each string in the array

• For each string, iterate through all possible substrings and check if it is a palindrome

• Keep track of the maximum length palindrome found

Compose multiple HOCs with render props in a React component

• Create a render prop component that accepts a function as a prop

• Wrap the render prop component with HOCs

• Pass the function as a prop to the HOCs

• Use the function to render the component's content

• Example: withAuth(withTheme(RenderPropComponent))

DELETE removes specific rows from a table, while TRUNCATE removes all rows and resets auto-increment values.

• DELETE is a DML command, while TRUNCATE is a DDL command.

• DELETE can be rolled back, while TRUNCATE cannot be rolled back.

• DELETE triggers ON DELETE triggers, while TRUNCATE does not trigger any triggers.

• DELETE is slower as it logs individual row deletions, while TRUNCATE is faster as it deallocates data pages.

• Example: DELETE FROM table_name WHERE condition; TRUNCATE tabl...read more

Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity. Denormalization is the opposite process.

• Normalization involves breaking down data into smaller, more manageable tables to reduce redundancy.

• Denormalization involves combining tables to improve query performance.

• Normalization helps maintain data integrity by reducing the risk of anomalies.

• Denormalization can improve read performance but may lead to data redundancy.

• Exa...read more

Java is not called the partial OOP concept.

• Java is a fully object-oriented programming language.

• It supports all the principles of OOP such as encapsulation, inheritance, and polymorphism.

• Java allows the creation of classes, objects, and methods to implement OOP concepts.

• It provides features like abstraction and encapsulation to achieve data hiding and modularity.

• Java also supports interfaces, which are a key component of OOP.

• The misconception of Java being a partial OOP conce...read more

Static polymorphism refers to the mechanism where the method to be called is determined at compile time.

• Method overloading is an example of static polymorphism where the method to be called is resolved at compile time based on the method signature.

• Compile-time polymorphism is another term for static polymorphism.

• Static polymorphism is achieved through function overloading and operator overloading.

Program to print the length of number of permutations of a given input

• Use recursion to generate all permutations

• Count the number of permutations and print the length

Swap 2 integers without using 3rd integer

• Use XOR operator

• Addition and subtraction can also be used

• Bitwise operations can be used

Java 8 features include lambda expressions, functional interfaces, streams, and default methods.

• Lambda expressions allow you to write code in a more concise and readable way.

• Functional interfaces are interfaces with a single abstract method, used for lambda expressions.

• Streams provide a way to work with sequences of elements and perform operations like filter, map, and reduce.

• Default methods allow interfaces to have method implementations.

• Example: (1) Lambda expression - (a, ...read more

Given an array of n-1 numbers 1<=a[i]<=n, find the missing number.

• Calculate the sum of all numbers from 1 to n using the formula n*(n+1)/2

• Calculate the sum of all elements in the array

• Subtract the sum of array elements from the sum of all numbers to get the missing number

Components are reusable UI elements in ReactJs. State is an object that stores data and controls a component's behavior.

• Components are like building blocks that can be combined to create complex UIs

• State is used to store and manage data within a component

• Changes to state trigger a re-render of the component

• State should be kept as minimal as possible to avoid performance issues

• Example: A button component can have a state that tracks the number of times it has been clicked

Private and special IP addresses are reserved ranges of IP addresses used for specific purposes.

• Private IP addresses are used within a private network and are not routable on the internet.

• Special IP addresses include loopback address (127.0.0.1) and broadcast address (255.255.255.255).

• Private IP ranges include 10.0.0.0 to 10.255.255.255, 172.16.0.0 to 172.31.255.255, and 192.168.0.0 to 192.168.255.255.

To reverse a string of a particular order separated by dots, split the string into an array, reverse the array, and join it back into a string.

• Split the string using the dot separator

• Reverse the resulting array

• Join the array back into a string using the dot separator

Key OOP concepts in Java include classes, objects, inheritance, polymorphism, encapsulation, and abstraction.

• Classes: Blueprint for creating objects, containing attributes and methods.

• Objects: Instances of classes that encapsulate data and behavior.

• Inheritance: Allows a class to inherit attributes and methods from another class.

• Polymorphism: Ability to present the same interface for different data types.

• Encapsulation: Bundling data and methods that operate on the data into a ...read more

The OSI Reference Model defines 7 layers that represent different functions in networking.

• Physical Layer - deals with physical connections and signals (e.g. cables, hubs)

• Data Link Layer - manages data transfer between devices on the same network (e.g. Ethernet)

• Network Layer - handles routing and forwarding of data packets (e.g. IP)

• Transport Layer - ensures reliable data delivery (e.g. TCP)

• Session Layer - establishes, maintains, and terminates connections (e.g. SSL)

• Presentatio...read more

To find leap year using single if condition

• Check if year is divisible by 4 and not divisible by 100

• Or check if year is divisible by 400

• If either of the above conditions is true, then it's a leap year

Distinct keyword in SQL is used to retrieve unique values from a column in a table.

• Distinct keyword eliminates duplicate rows from the result set

• It is often used in conjunction with SELECT statement

• Example: SELECT DISTINCT column_name FROM table_name

Use concatenation operator to add two strings.

• Use '+' operator to concatenate two strings.

• Example: str1 + str2 will result in '12348765'.

I would use a combination of HTML, CSS, and JavaScript to create a simple web application that stores and displays data.

• Use HTML to create the structure of the web application

• Use CSS to style the elements on the page

• Use JavaScript to handle user interactions and store/retrieve data

• Consider using a backend server (e.g. Node.js) to handle data storage and retrieval

• Utilize AJAX to fetch data from the server asynchronously

setTimeout, setImmediate and process.nextTick are Node.js functions used for asynchronous programming.

• setTimeout is used to execute a function after a specified amount of time has passed.

• setImmediate is used to execute a function immediately after the current event loop iteration.

• process.nextTick is used to execute a function at the beginning of the next event loop iteration.

• setTimeout and setImmediate are similar, but setImmediate has higher priority in the event loop.

• proces...read more

I used the Dijkstra's algorithm for finding the shortest path in my project.

• Implemented Dijkstra's algorithm to find the shortest path between nodes in a graph

• Used priority queue to optimize the algorithm

• Considered edge weights and node distances while calculating the shortest path

ReactJS life cycle refers to the series of methods that are invoked in the process of creating, updating and destroying a component.

• ReactJS life cycle consists of three phases: Mounting, Updating and Unmounting.

• Mounting phase includes methods like constructor, render, componentDidMount.

• Updating phase includes methods like shouldComponentUpdate, render, componentDidUpdate.

• Unmounting phase includes method componentWillUnmount.

• These methods help in managing the state and props o...read more

Reverse a string using array manipulation

• Create an array of characters from the input string

• Use a loop to iterate through the array in reverse order

• Append each character to a new string to form the reversed string

Method overloading involves multiple methods in the same class with the same name but different parameters. Method overriding involves a subclass providing a specific implementation of a method that is already provided by its superclass.

• Method overloading is achieved within the same class by having multiple methods with the same name but different parameters.

• Method overriding occurs in a subclass that provides a specific implementation of a method that is already provided by ...read more

getDerivedStateFromProps() updates state based on props changes. getSnapshotBeforeUpdate() captures current state before update.

• getDerivedStateFromProps() is called before rendering and updates state based on changes in props.

• getSnapshotBeforeUpdate() is called after rendering but before updating the DOM. It captures current state before update.

• getDerivedStateFromProps() is a static method and should return an object to update state or null to indicate no update.

• getSnapshotBe...read more

Integrity constraints are rules that ensure data integrity and consistency in a database.

• Integrity constraints are used to enforce business rules or data quality rules in a database.

• They can include rules such as unique constraints, foreign key constraints, and check constraints.

• Unique constraints ensure that no two rows have the same value in a specified column.

• Foreign key constraints enforce referential integrity by ensuring that values in one table match values in another ...read more

Exception handling is a mechanism to handle runtime errors in a program to prevent it from crashing.

• Exceptions are unexpected events that occur during the execution of a program.

• Exception handling allows the programmer to gracefully handle these errors and prevent the program from crashing.

• Common exception handling constructs include try, catch, and finally blocks.

• Example: try { // code that may throw an exception } catch(Exception e) { // handle the exception }

• Example: final...read more

Inheritance is a mechanism where a new class is derived from an existing class. Encapsulation is the process of hiding implementation details from the user.

• Inheritance allows the new class to inherit properties and methods of the existing class.

• Encapsulation helps in achieving data abstraction and security.

• Inheritance promotes code reusability while encapsulation promotes data security.

• Example of inheritance: class Car extends Vehicle

• Example of encapsulation: private variable...read more

Code to merge two sorted arrays

• Create a new array to store the merged result

• Use two pointers to iterate through both arrays and compare elements

• Add the smaller element to the new array and move the pointer for that array

OOPS Concepts are fundamental principles of Object-Oriented Programming.

• Encapsulation - bundling of data and methods that operate on that data

• Inheritance - ability of a class to inherit properties and methods from its parent class

• Polymorphism - ability of objects to take on multiple forms

• Abstraction - hiding of complex implementation details from the user

• Example code: class Car { private String make; public void setMake(String make) { this.make = make; } }

Local Storage, Session Storage, and Cache are used to store data in the browser for faster access and better user experience.

• Local Storage: stores data with no expiration date and can be accessed across multiple windows and tabs

• Session Storage: stores data for a single session and is cleared when the session ends

• Cache: stores data temporarily to reduce server load and improve performance

• Examples: storing user preferences, caching images and scripts for faster page load

Databases are essential for storing, organizing, and retrieving large amounts of data efficiently.

• Databases provide a structured way to store and manage data.

• They allow for efficient retrieval of data through queries.

• Databases can handle large amounts of data and ensure data integrity.

• They enable multiple users to access and modify data simultaneously.

• Examples include MySQL, Oracle, MongoDB, and SQL Server.