100+ Interview Questions and Answers

Interview questions for Software Engineer position

• Array manipulation and linked list operations

• Tree data structure and balancing techniques

• Database concepts and differences between SQL and NoSQL

• Web development frameworks and protocols

• Concepts of Deadlock and Race Condition

• Use of pointers in function oriented programming and their absence in Java

Yes, a constructor can be made private in C++ to restrict object creation outside the class.

• Private constructors are used in Singleton design pattern to ensure only one instance of the class is created.

• If a constructor is made private, it can only be accessed by the member functions of the class.

• Attempting to create an object of a class with a private constructor outside the class will result in a compile-time error.

Binary Tree is a tree data structure where each node has at most two children. Binary Search Tree is a binary tree with the property that the left subtree of a node contains only nodes with keys lesser than the node's key and the right subtree of a node contains only nodes with keys greater than the node's key.

• Binary Tree can have any values in the nodes, while Binary Search Tree has a specific order of values.

• Binary Search Tree allows for efficient searching, insertion, and ...read more

DLL is a library of executable functions and data that can be used by a Windows application.

• DLLs are loaded at runtime and can be shared by multiple applications.

• They allow for modular programming and reduce memory usage.

• DLLs can be used for device drivers, system utilities, and application extensions.

• Examples of DLLs include kernel32.dll, user32.dll, and msvcr100.dll.

Function pointers are pointers that point to the memory address of a function. They can be passed as arguments or returned from a function.

• Function pointers allow for dynamic function calls at runtime

• Function pointers can be used to implement callbacks

• Function pointers can be used to implement polymorphism

• Normal functions are called directly, while function pointers are called indirectly

• Function pointers can be assigned to NULL to indicate that they do not point to a valid fu...read more

Diamond problem occurs in multiple inheritance when two base classes have a common method. It is solved using virtual inheritance.

• Diamond problem occurs when a derived class inherits from two base classes that have a common method.

• Virtual inheritance is used to solve the diamond problem.

• Virtual inheritance ensures that only one instance of the common base class is created.

Ways to prevent instantiation of a class

• Declare the class as abstract

• Make the constructor private

• Implement a static factory method

• Throw an exception in the constructor

• Use the Singleton pattern

The task is to find any number of elements in an array that add up to a given target.

• Use a recursive approach to find all possible combinations of elements that add up to the target.

• Start with the first element and recursively call the function with the remaining elements and the reduced target.

• If the target becomes zero, add the current combination to the result.

• If the target becomes negative or there are no more elements, backtrack and try the next element.

• Return all the co...read more

Separate negative and positive numbers in a linked list.

• Create two separate linked lists for positive and negative numbers

• Traverse the original linked list and add nodes to respective lists

• Join the two lists to get the final linked list with separated numbers

Printing names of 4 threads in a given order using an array of strings.

• Create an array of strings with the names of the threads in the desired order.

• Use a loop to iterate through the array and print each thread name.

• Ensure that the threads are started in the same order as the names in the array.

Delete Kth node from end of linked list in single iteration

• Use two pointers, one to traverse the list and another to keep track of Kth node from end

• Move both pointers simultaneously until the first pointer reaches the end

• Delete the Kth node from end using the second pointer

Segregate 0's and 1's in array using Dutch National Flag Algorithm

• Use three pointers - low, mid, and high

• low points to the first index of 1

• mid points to the first index of unknown element

• high points to the last index of 1

• If arr[mid] is 0, swap arr[low] and arr[mid], increment low and mid

• If arr[mid] is 1, increment mid

• If arr[mid] is 2, swap arr[mid] and arr[high], decrement high

Equal Sum Partition problem with DP and matrix printing

• The problem involves dividing an array into two subsets with equal sum

• Dynamic programming can be used to solve this problem efficiently

• A matrix can be used to keep track of the subsets

• Printing the subsets can be done by backtracking through the matrix

I would have pursued a career in music.

• I have been playing the guitar for over 10 years.

• I have performed at local gigs and events.

• I enjoy writing and composing my own music.

To check for a loop in a linked list, we use the Floyd's cycle-finding algorithm.

• Create two pointers, slow and fast, and initialize them to the head of the linked list.

• Move slow pointer by one node and fast pointer by two nodes.

• If there is a loop, the two pointers will eventually meet.

• If there is no loop, the fast pointer will reach the end of the linked list.

• Time complexity of this algorithm is O(n) and space complexity is O(1).

Find the maximum multiplication of 3 numbers in an array of strings.

• Convert the array of strings to an array of integers.

• Sort the array in descending order.

• Check the product of first three elements and last two elements with the first element.

Finally is a block of code that executes after try-catch block. It will not execute if System.exit() is called.

• Finally block is used to execute a block of code after try-catch block

• It will execute even if an exception is thrown

• Finally block will not execute if the JVM exits before the block is executed

• System.exit() terminates the JVM and finally block will not execute

Developed a project management tool for tracking tasks and deadlines.

• Implemented user authentication and authorization for secure access.

• Utilized a relational database to store project data and user information.

• Designed a user-friendly interface with drag-and-drop functionality for task management.

To check if a linked list is circular, we can use Floyd's cycle-finding algorithm.

• Create two pointers, slow and fast, and initialize them to the head of the linked list

• Move slow pointer by one node and fast pointer by two nodes

• If the linked list is circular, the fast pointer will eventually catch up to the slow pointer

• If the linked list is not circular, the fast pointer will reach the end of the list

• Time complexity: O(n), Space complexity: O(1)

Remove duplicates from Linked List. Both variants.

• Variant 1: Using Hash Set to keep track of visited nodes and removing duplicates

• Variant 2: Using two pointers to compare each node with all subsequent nodes and removing duplicates

• Example: 1->2->3->2->4->3, Output: 1->2->3->4

Calculating the depth of a tree

• Depth of a tree is the maximum distance from the root node to any leaf node

• Can be calculated recursively by finding the maximum depth of left and right subtrees

• Base case is when the node is null, return 0

Registers are small, fast memory locations in a CPU that store data for quick access.

• Registers are used to store data that is frequently accessed by the CPU.

• They are faster than accessing data from RAM.

• Registers are limited in number and size.

• Examples of registers include the program counter, stack pointer, and general-purpose registers.

• Register usage can be optimized for performance in code.

• Accessing registers can be done using assembly language.

• In C++, registers can be decl...read more

Level order traversal is a tree traversal algorithm that visits nodes level by level.

• Start at the root node and visit all nodes at the current level before moving to the next level

• Use a queue to keep track of nodes at each level

• Enqueue the root node, then dequeue and visit each node while enqueueing its children

• Repeat until the queue is empty

• Time complexity: O(n), space complexity: O(w) where w is the maximum width of the tree

Reverse a linked list in groups of k

• Create a function to reverse a linked list

• Iterate through the linked list in groups of k

• Reverse each group using the function

• Connect the reversed groups back together

• Return the new head of the linked list

Encapsulation is a mechanism of wrapping data and code together into a single unit.

• Encapsulation helps in achieving data hiding and abstraction.

• It provides better control over the data by making it private and accessible only through public methods.

• Real-time examples of encapsulation include a car's engine, which is encapsulated and can only be accessed through the car's interface.

• Another example is a mobile phone, where the internal components are encapsulated and can only b...read more

Runtime polymorphism is the ability of an object to take on multiple forms during runtime.

• It is achieved through method overriding

• It allows for more flexibility and extensibility in code

• It is a key feature of object-oriented programming

• Example: Animal class with different subclasses such as Dog, Cat, and Bird

Count the number of occurrences of each character in a given string.

• Create a dictionary to store the count of each character.

• Iterate through the string and update the count in the dictionary.

• Return the dictionary with character count.

Inheritance allows a subclass to inherit properties and methods from a superclass, but it has some disadvantages.

• Inheritance can lead to tight coupling between classes, making it difficult to modify the superclass without affecting the subclass.

• Inheritance can also lead to the creation of deep class hierarchies, which can be difficult to understand and maintain.

• Inheritance can result in code duplication if multiple subclasses need to override the same method or property.

• Inher...read more

The Dutch national flag problem is a sorting problem that involves sorting an array of 3 distinct values.

• The problem involves sorting an array of 3 distinct values: red, white, and blue.

• The goal is to sort the array in-place, without using any additional data structures.

• The solution involves using three pointers to keep track of the boundaries between the different values.

Merge two sorted linked lists

• Create a new linked list

• Compare the first nodes of both lists and add the smaller one to the new list

• Move the pointer of the added node to the next node in the list

• Repeat until one of the lists is empty

• Add the remaining nodes of the non-empty list to the new list

Program to find all palindromic strings in a given string.

• Iterate through the string and check for palindromic substrings using two pointers.

• Add the palindromic substrings to an array of strings.

• Return the array of palindromic strings.

Use tree traversal to find the minimum number in a tree structure.

• Start at the root node and compare it with its children to find the minimum value.

• Use depth-first search or breadth-first search to traverse the tree.

• Keep track of the minimum value found so far as you traverse the tree.

• Consider implementing a recursive function to traverse the tree efficiently.

Merge Sort is a divide-and-conquer algorithm that recursively divides an array into two halves, sorts them, and then merges them.

• Divide the array into two halves

• Recursively sort each half

• Merge the sorted halves

SQL query to find the 2nd highest salary in a table.

• Use ORDER BY and LIMIT to sort and select the 2nd highest salary.

• Use subquery to avoid duplicates if necessary.

Code to split an array of integers into two subarrays with equal sum.

• Iterate through the array and calculate the total sum.

• Divide the sum by 2 to get the target sum for each subarray.

• Use dynamic programming to find a subset of the array that adds up to the target sum.

• Return the two subarrays.

• Example: [1, 2, 3, 4, 5, 6] -> [1, 2, 3, 6], [4, 5]

• Example: [1, 2, 3, 4, 5] -> [1, 4, 5], [2, 3]

Method overriding is a feature in object-oriented programming where a subclass provides a specific implementation of a method that is already provided by its parent class.

• Occurs when a subclass provides a specific implementation of a method that is already provided by its parent class

• The method in the subclass must have the same name, return type, and parameters as the method in the parent class

• Allows for polymorphism, where a subclass can be treated as an instance of its par...read more

Java is a popular programming language known for its platform independence and object-oriented features.

• Platform independence allows Java code to run on any platform without recompilation

• Object-oriented features like encapsulation, inheritance, and polymorphism make code modular and reusable

• Java has a vast standard library with built-in support for networking, I/O, and concurrency

• Java is highly secure with features like bytecode verification and automatic memory management

Implementing a binary search tree and its traversal methods.

• Start by defining a Node class with left and right child pointers.

• Implement insert() method to add nodes to the tree.

• Implement inorder(), preorder(), and postorder() traversal methods.

• Implement search() method to find a node in the tree.

• Implement delete() method to remove a node from the tree.

• Consider edge cases like empty tree, duplicate nodes, etc.

Find the length of the longest subsequence of contiguous integers in an array.

• Sort the array

• Iterate through the array and check for consecutive integers

• Keep track of the longest subsequence found

Use flatMap and map to extract list of pincodes from Employee objects

• Use flatMap to flatten the list of Addresses in each Employee object

• Use map to iterate over the flattened list and extract the pincodes

• Example: employeeList.stream().flatMap(emp -> emp.getAddresses().stream()).map(address -> address.getPincode()).collect(Collectors.toList())

Database pooling is a technique used to manage a pool of database connections for efficient resource utilization. HikariCP is a popular database connection pooling library in Java.

• HikariCP is a high-performance database connection pooling library for Java applications.

• It is known for its low latency and high throughput.

• Configurations for HikariCP include settings such as maximum pool size, connection timeout, and idle timeout.

• Example: HikariConfig config = new HikariConfig();...read more

DBMS types include relational, NoSQL, object-oriented, and hierarchical. Each has unique features and use cases.

• Relational DBMS: structured data, ACID compliance, SQL queries (e.g. MySQL, Oracle)

• NoSQL DBMS: unstructured data, flexible schema, horizontal scaling (e.g. MongoDB, Cassandra)

• Object-oriented DBMS: data stored as objects, supports inheritance and polymorphism (e.g. db4o)

• Hierarchical DBMS: data organized in a tree-like structure, good for storing nested data (e.g. IBM...read more

Code a system to query an API, do multiprocessing and improve efficiency

• Use a library like requests in Python to query the API

• Implement multiprocessing using a library like multiprocessing or threading in Python

• Optimize efficiency by caching API responses or using asynchronous programming

Conditions for a deadlock in software engineering

• Deadlock occurs when each process in a set is waiting for an event that only another process in the set can cause

• Four conditions for a deadlock: mutual exclusion, hold and wait, no preemption, circular wait

• Example: Process A holds resource X and waits for resource Y, while Process B holds resource Y and waits for resource X

Find unique characters in a window of k size in a string.

• Use a sliding window approach.

• Maintain a hash table to keep track of character frequency.

• Remove characters from hash table as the window slides.

Find maximum for each contiguous subarray of size k from an array of size n.

• Iterate through the array and keep track of maximum for each subarray of size k

• Use a sliding window approach to efficiently calculate maximum for each subarray

• Time complexity: O(n)

• Example: arr = [10, 5, 2, 7, 1, 9, 4], k = 3, output = [10, 7, 7, 9, 9]

OOPs concepts are the fundamental principles of object-oriented programming.

• Abstraction

• Encapsulation

• Inheritance

• Polymorphism

Convert given no to corresponding excel no.

• Excel no starts from 1 and goes up to 16384

• Excel no is calculated using column and row numbers

• For example, 1 corresponds to A, 27 corresponds to AA, 28 corresponds to AB, and so on

To troubleshoot an internet issue, check the connection, restart the router, check for software issues, and contact the service provider if needed.

• Check the physical connection of the router and modem

• Restart the router and modem

• Check for any software issues on the device (e.g. network settings, firewall)

• Contact the internet service provider for further assistance

The program finds repeating characters in a given string.

• Iterate through each character in the string

• Store each character in a data structure

• If a character is already present in the data structure, it is a repeating character

To find the second highest salary from employees table and traverse a binary tree in pre-order, in-order, and post-order.

• To find the second highest salary, you can use a subquery or window function like ROW_NUMBER() or DENSE_RANK().

• For pre-order traversal, visit the root node first, then recursively do a pre-order traversal of the left subtree, followed by the right subtree.

• For in-order traversal, recursively do an in-order traversal of the left subtree, visit the root node, ...read more

Implement merge sort and find kth largest element in an array.

• Merge sort is a divide and conquer algorithm that recursively divides the array into two halves, sorts them and then merges them.

• Kth largest element can be found using quick select algorithm or by sorting the array and returning the kth element from the end.

• Merge sort has a time complexity of O(nlogn) and space complexity of O(n).

• Quick select has a time complexity of O(n) in average case and O(n^2) in worst case.

• So...read more

Props are inputs passed to React components. There are two types: ownProps and childrenProps.

• ownProps are passed directly to the component from its parent

• childrenProps are passed to the component through its children

• ownProps can be accessed using this.props in the component

• childrenProps can be accessed using this.props.children in the component

Singleton is a creational design pattern that ensures a class has only one instance and provides a global point of access to it.

• To create a Singleton, make the constructor private to prevent direct instantiation

• Create a static method that returns the instance of the class

• Use lazy initialization to create the instance only when it's needed

• Ensure thread safety by using synchronized keyword or double-checked locking

• Examples: java.lang.Runtime, java.awt.Desktop, java.util.Calenda...read more

Joins are used to combine data from two or more tables based on a related column.

• Joins are useful for retrieving data from multiple tables that have a relationship.

• There are different types of joins such as inner join, left join, right join, and full outer join.

• Inner join returns only the matching rows from both tables.

• Left join returns all the rows from the left table and matching rows from the right table.

• Right join returns all the rows from the right table and matching row...read more

Segregate an array of 0s and 1s with minimum swaps.

• Count the number of 0s in the array.

• Swap the 1s with the 0s until all 0s are on one side and 1s on the other.

• The minimum number of swaps required is half the number of 1s on the side with fewer 1s.

Singleton design pattern restricts the instantiation of a class to one object.

• Ensures only one instance of a class exists

• Provides a global point of access to that instance

• Used when only one instance of a class is needed throughout the application

• Example: Database connection manager

I suggest using a hybrid automation framework for testing Amazon application.

• Use Selenium WebDriver for web automation

• Use Appium for mobile automation

• Use TestNG for test management and reporting

• Use Page Object Model for better code maintenance

• Use data-driven approach for test data management

• Use Jenkins for continuous integration and deployment

Add two linked lists representing numbers and return the resulting linked list.

• Traverse both linked lists and add the corresponding digits, keeping track of carry.

• Create a new node for each digit and update the carry for the next iteration.

• If one list is longer than the other, add the remaining digits to the result.

• Handle the case where the carry is not zero after all digits have been added.

• Time complexity: O(max(m,n)), where m and n are the lengths of the input lists.

I remain calm, listen actively, empathize with their situation, apologize for any inconvenience, and work towards finding a solution.

• Remain calm and composed

• Listen actively to understand their concerns

• Empathize with their situation

• Apologize for any inconvenience caused

• Work towards finding a solution to address their issue

My approach to building basic logic skills involves practicing problem-solving exercises, breaking down complex problems into smaller parts, and seeking feedback to improve.

• Practice problem-solving exercises regularly to strengthen logical thinking abilities.

• Break down complex problems into smaller, more manageable parts to better understand the problem and find solutions.

• Seek feedback from peers or mentors to identify areas for improvement and refine logic skills.

• Utilize res...read more

Use binary search to find the first and last occurrence of the character, then calculate the frequency.

• Use binary search to find the first occurrence of the character in the string.

• Use binary search to find the last occurrence of the character in the string.

• Calculate the frequency by subtracting the indices of the last and first occurrences and adding 1.

Method overriding in Java with code example

• Output will be 'Child class method' as the method in Child class overrides the method in Parent class

• Method overriding is a feature that allows a subclass to provide a specific implementation of a method that is already provided by its superclass

• The method in the subclass should have the same name, return type, and parameters as the method in the superclass

OOPs concepts and pillars. Design a Vehicle class based on requirements.

• OOPs concepts: Abstraction, Encapsulation, Inheritance, Polymorphism

• Vehicle class requirements: attributes like make, model, year, methods like start, stop, accelerate