Celestial Systems IT Infrastructure Lead Interview Questions, Process, and Tips

Round duration - 90 minutes
Round difficulty - Easy

It was on online objective test consisting of 4 sections: Aptitude, Technical MCQs, Code snippet based MCQs and Coding part.

Q1. 
Valid Parentheses Problem Statement
Given a string 'STR' consisting solely of the characters “{”, “}”, “(”, “)”, “[” and “]”, determine if the parentheses are balanced.
Input:
The first line contains an...read more
Ans. 
The task is to determine if a given string of parentheses is balanced or not.
• Iterate through the characters of the string and use a stack to keep track of opening parentheses.

• When encountering an opening parenthesis, push it onto the stack. When encountering a closing parenthesis, check if it matches the top of the stack.

• If the stack is empty at the end or there are unmatched parentheses, the string is not balanced.

• Exa...read more
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Q2. 
Palindrome Linked List Problem Statement
Determine if a given singly linked list of integers is a palindrome. Return true if it is a palindrome, otherwise return false.
Example:
Input:
1 -> 2 -> ...read more
Ans. 
Check if a given singly linked list of integers is a palindrome.
• Use two pointers to find the middle of the linked list.

• Reverse the second half of the linked list.

• Compare the first half with the reversed second half to determine if it is a palindrome.
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Round duration - 60 minutes
Round difficulty - Easy

This was a technical and managerial round. The interviewer gave me a situation where I am in testing team and I found that customer requirement was drop down list at a place but developer has used bullet selection, and is not ready to change it. How will you manage? I gave some good replies and he was convinced.

Q1. What is a virtual function?
Ans. 
A virtual function is a function in a base class that is declared using the keyword 'virtual' and can be overridden by a function with the same signature in a derived class.
• Virtual functions allow for dynamic polymorphism in object-oriented programming.

• They are used to achieve runtime polymorphism by enabling late binding.

• Virtual functions are declared in a base class and can be overridden in derived classes.

• Example: v...read more
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Q2. Can you explain how to perform a level order traversal of a binary tree in spiral form?
Ans. 
Level order traversal of a binary tree in spiral form involves alternating between left and right while traversing each level.
• Start by pushing the root node into a queue.

• While the queue is not empty, pop a node, print its value, and push its children into the queue.

• For each level, alternate between popping nodes from the queue and printing their values from left to right or right to left.

• Continue this process until all
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Q3. What are abstract classes in C++?
Ans. 
Abstract classes in C++ are classes that cannot be instantiated and are designed to be base classes for other classes.
• Abstract classes may contain pure virtual functions, making them incomplete and unable to be instantiated.

• Derived classes must implement all pure virtual functions from the abstract class in order to be concrete classes.

• Abstract classes can have non-virtual functions and member variables like regular cl...read more
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Round duration - 60 minutes
Round difficulty - Easy

This was also a technical round. He asked to optimize the code I wrote in coding round. Then he asked me a few puzzles and questions on OOPS, OS and DBMS.

Q1. Can you explain the ACID properties in the context of database management systems?
Ans. 
ACID properties are a set of properties that guarantee the reliability of transactions in database management systems.
• ACID stands for Atomicity, Consistency, Isolation, and Durability.

• Atomicity ensures that either all operations in a transaction are completed successfully or none of them are.

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

• Isolation ensures that the e...read more
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Q2. What is the difference between paging and segmentation in operating systems?
Ans. 
Paging and segmentation are memory management techniques in operating systems.
• Paging divides physical memory into fixed-size blocks called pages, while segmentation divides logical memory into variable-size segments.

• Paging allows for efficient memory allocation and management, while segmentation provides protection and sharing of memory.

• Paging is simpler to implement but can lead to internal fragmentation, while segmen...read more
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Q3. What is concurrency control?
Ans. 
Concurrency control is a technique used in databases to manage simultaneous access and modification of data by multiple users or processes.
• Concurrency control ensures that transactions are executed in a way that maintains data consistency and integrity.

• Techniques like locking, timestamp ordering, and optimistic concurrency control are used to implement concurrency control.

• For example, in a banking system, concurrency c...read more
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Q4. What is the difference between String Buffer and String Builder in Java?
Ans. 
String Buffer is synchronized and thread-safe, while String Builder is not synchronized and faster.
• String Buffer is synchronized, making it thread-safe for use in multi-threaded environments.

• String Builder is not synchronized, resulting in faster performance but not thread-safe.

• String Builder is preferred for single-threaded operations, while String Buffer is preferred for multi-threaded operations.
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Q5. What are smart pointers in C++?
Ans. 
Smart pointers in C++ are objects that act like pointers but provide automatic memory management.
• Smart pointers help prevent memory leaks by automatically managing memory allocation and deallocation.

• Examples include unique_ptr, shared_ptr, and weak_ptr.

• unique_ptr is used for exclusive ownership, shared_ptr for shared ownership, and weak_ptr to prevent circular references.
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Q6. What is the difference between a mutex and a semaphore?
Ans. 
Mutex is used for exclusive access to a resource, while semaphore is used for controlling access to a resource by multiple threads.
• Mutex is binary and allows only one thread to access the resource at a time.

• Semaphore can have a count greater than one, allowing multiple threads to access the resource simultaneously.

• Mutex is typically used for protecting critical sections of code, while semaphore is used for synchronizat...read more
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