McKinsey & Company Senior Software Engineer Interview Questions and Answers

Round duration - 60 Minutes
Round difficulty - Medium

This round had 1 question of Basic Programming and Maths and then I was asked some questions related to DBMS and basic C++ concepts.

Q1. 
Find Terms of Series Problem
Ayush is tasked with determining the first 'X' terms of the series defined by 3 * N + 2, ensuring that no term is a multiple of 4.
Input:
The first line contains a single in...read more
Ans. 
Generate the first 'X' terms of a series 3 * N + 2, excluding multiples of 4.
• Iterate through numbers starting from 1 and check if 3 * N + 2 is not a multiple of 4.

• Keep track of the count of terms generated and stop when 'X' terms are found.

• Return the list of terms that meet the criteria for each test case.
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Q2. Why is normalization needed in a database?
Ans. 
Normalization is needed in a database to reduce redundancy, improve data integrity, and optimize database performance.
• Eliminates data redundancy by breaking down data into smaller, more manageable tables

• Prevents update anomalies by ensuring data consistency

• Improves data integrity by enforcing relationships between tables

• Optimizes database performance by reducing storage space and improving query efficiency
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Q3. Explain the difference between intension and extension in a database.
Ans. 
Intension refers to the attributes or properties of a concept, while extension refers to the instances or examples of that concept in a database.
• Intension describes the characteristics or properties of a concept.

• Extension refers to the actual instances or examples of that concept.

• For example, in a database of fruits, intension would include attributes like color, taste, and size, while extension would list specific fru
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Q4. What is the difference between new() and malloc() in C++?
Ans. 
new() is used to allocate memory for an object and call its constructor, while malloc() is used to allocate memory without calling any constructor.
• new() is a C++ operator, while malloc() is a function in C.

• new() returns a pointer to the allocated memory, while malloc() returns a void pointer.

• new() automatically calls the constructor of the object, while malloc() does not initialize the allocated memory.

• Example: int* ...read more
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Q5. What distinguishes a structure from a class in C++?
Ans. 
In C++, a structure is a user-defined data type that can hold both data and functions, while a class can also have access specifiers and inheritance.
• Structures in C++ are primarily used for grouping data members together, while classes can have additional features like access specifiers (public, private, protected) and inheritance.

• Structures default to public access for their members, while classes default to private a...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This round was preety much mixed and contained questions from Operating Systems, Unix, Java and more importantly Selenium.

Q1. Can you explain piping in Unix/Linux?
Ans. 
Piping in Unix/Linux allows the output of one command to be used as the input for another command.
• Piping is done using the '|' symbol.

• It helps in connecting multiple commands together to perform complex operations.

• Example: ls -l | grep 'txt' - This command lists all files in long format and then filters for files with 'txt' in their name.
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Q2. What is memory protection in operating systems?
Ans. 
Memory protection in operating systems is a feature that prevents a process from accessing memory that has not been allocated to it.
• Memory protection helps prevent one process from interfering with the memory of another process.

• It ensures that each process can only access memory that has been allocated to it.

• Examples of memory protection mechanisms include read-only memory segments and memory segmentation.

• Memory protec...read more
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Q3. What happens if the static modifier is not included in the main method signature in Java?
Ans. 
The main method in Java must include the static modifier to be able to run the program.
• Without the static modifier, the main method cannot be called by the Java Virtual Machine (JVM).

• The program will not be able to start and will throw a NoSuchMethodError.

• Adding the static modifier allows the main method to be called without creating an instance of the class.
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Q4. Can you tell us something about the JIT compiler?
Ans. 
JIT compiler stands for Just-In-Time compiler, which compiles code during runtime for improved performance.
• JIT compiler translates bytecode into machine code on-the-fly

• It helps in optimizing performance by compiling frequently executed code paths

• Examples include Java HotSpot VM's JIT compiler and .NET's JIT compiler
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Q5. What is XPath?
Ans. 
XPath is a query language used for selecting nodes from an XML document.
• XPath stands for XML Path Language

• It is used to navigate through elements and attributes in an XML document

• XPath uses path expressions to select nodes or content in an XML document

• Example: //book[@category='fiction'] selects all book elements with category attribute equal to 'fiction'
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Q6. Can you explain the pause feature in Selenium IDE?
Ans. 
The pause feature in Selenium IDE allows users to pause the execution of a test case for a specified amount of time.
• The pause command is used to introduce a delay in the test execution.

• It takes a parameter specifying the time to pause in milliseconds.

• For example, 'pause 3000' will pause the test execution for 3 seconds.
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Q7. What are the four parameters that you need to pass in Selenium?
Ans. 
The four parameters needed to pass in Selenium are URL, Port Number, Browser Driver, and Desired Capabilities.
• URL: The URL of the website you want to automate testing on.

• Port Number: The port number where the Selenium server is running.

• Browser Driver: The specific browser driver (e.g. ChromeDriver, GeckoDriver) to use for testing.

• Desired Capabilities: Additional settings and preferences for the browser driver.
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Round duration - 30 Minutes
Round difficulty - Easy

This was a typical HR round with some standard Behavioral questions.

Round duration - 60 Minutes
Round difficulty - Easy

This round consisted of 1 question from DSA with easy level of difficulty and then the rest of the questions were asked from DBMS and SQL.

Q1. 
Trailing Zeros in Factorial Problem
Find the number of trailing zeroes in the factorial of a given number N.
Input:
The first line contains an integer T representing the number of test cases.
Each of the...read more
Ans. 
Count the number of trailing zeros in the factorial of a given number N.
• Iterate through each test case and calculate the factorial of N.

• Count the number of trailing zeros by dividing the factorial by 10 until the remainder is not 0.

• Return the count of trailing zeros for each test case.
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Q2. Can you explain the concept of ACID properties in DBMS?
Ans. 
ACID properties in DBMS ensure data integrity and consistency.
• ACID stands for Atomicity, Consistency, Isolation, and Durability.

• Atomicity ensures that all operations in a transaction are completed successfully or none at all.

• Consistency ensures that the database remains in a valid state before and after the transaction.

• Isolation ensures that multiple transactions can run concurrently without affecting each other.

• Durabi...read more
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Q3. What is meant by normalization and denormalization?
Ans. 
Normalization is organizing data in a database to reduce redundancy and improve data integrity. Denormalization is adding redundant data to improve read performance.
• Normalization is the process of organizing data in a database to reduce redundancy and dependency by dividing the data into multiple tables and defining relationships between them.

• Denormalization is the process of adding redundant data to one or more tables...read more
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Q4. How do you take a backup of a table in MySQL?
Ans. 
Use the mysqldump command to take a backup of a table in MySQL.
• Use the mysqldump command followed by the database name and table name to take a backup of a specific table.

• Specify the username and password for the MySQL database using the -u and -p flags.

• Redirect the output of the mysqldump command to a file to save the backup.
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Round duration - 60 Minutes
Round difficulty - Medium

This round had questions revolving around Java and Selenium. Core concpets of Selenium were very frequent in
this interview.

Q1. What is a JIT compiler?
Ans. 
JIT compiler stands for Just-In-Time compiler, which compiles code during runtime instead of ahead of time.
• JIT compiler converts bytecode into machine code on-the-fly

• Improves performance by optimizing frequently executed code

• Examples include Java HotSpot, .NET CLR
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Q2. What are the advantages of using Packages in Java?
Ans. 
Packages in Java help organize and manage classes and interfaces, provide access control, and prevent naming conflicts.
• Organize classes and interfaces into a single unit for better maintainability

• Provide access control by using access modifiers like public, private, protected, and default

• Prevent naming conflicts by using unique package names

• Facilitate modular programming and code reusability
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Q3. What is the difference between assert and verify commands in Selenium?
Ans. 
Assert commands in Selenium are used to verify the expected result of a test case, while verify commands are used to check for the presence of an element without halting the test execution.
• Assert commands halt the test execution if the verification fails, while verify commands continue with the test execution even if the verification fails.

• Assert commands are used to validate the expected result of a test case, while v...read more
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Q4. When should I use Selenium Grid?
Ans. 
Selenium Grid is used for parallel testing across multiple browsers, devices, and operating systems.
• Use Selenium Grid when you need to run tests in parallel to save time.

• It is useful for testing on multiple browsers, devices, and operating systems simultaneously.

• Helps in reducing test execution time by distributing tests across multiple nodes.

• Useful for large test suites that require testing on various configurations.

• C...read more
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Q5. What are the different types of waits available in Selenium WebDriver?
Ans. 
Different types of waits in Selenium WebDriver include Implicit Wait, Explicit Wait, and Fluent Wait.
• Implicit Wait: Waits for a certain amount of time before throwing a NoSuchElementException.

• Explicit Wait: Waits for a certain condition to occur before proceeding further in the code.

• Fluent Wait: Waits for a condition to be true with a specified polling frequency and timeout.
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Round duration - 30 Minutes
Round difficulty - Easy

This is a cultural fitment testing round .HR was very frank and asked standard questions. Then we discussed about my role.

Q1. Why should we hire you?
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Q2. Why are you looking for a job change?
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