Fidelity Investments Principal Software Development Engineer In Test Interview Questions and Answers

Q1. Tell me about yourself
Ans. 
I am a passionate software engineer with experience in developing web applications using various technologies.
• Experienced in developing web applications using HTML, CSS, JavaScript, and frameworks like React and Angular

• Proficient in backend development with Node.js and databases like MySQL and MongoDB

• Familiar with version control systems like Git and deployment tools like Docker
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Q1. Tell me about yourself
Ans. 
I am a software engineer with 5 years of experience in developing web applications using Java, Spring Boot, and Angular.
• 5 years of experience in software development

• Proficient in Java, Spring Boot, and Angular

• Strong problem-solving skills

• Experience working in Agile development environment

• Passionate about learning new technologies
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Q1. How would you design tiny url implementation?
Ans. 
Design a system to create and manage short URLs for long URLs.
• Use a database to store mappings of short URLs to long URLs.

• Generate a unique short URL for each long URL using a hashing algorithm.

• Implement a redirect service to redirect users from short URLs to long URLs.

• Consider adding expiration dates for short URLs to manage storage.

• Implement analytics to track usage of short URLs.
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Round duration - 60 minutes
Round difficulty - Medium

Technical round with questions on DSA and OS.

Q1. 
LRU Cache Design Problem Statement
Design and implement a data structure for a Least Recently Used (LRU) cache that supports the following operations:
• get(key) - Retrieve the value associated with the...read more
Ans. 
Design and implement a Least Recently Used (LRU) cache data structure that supports get and put operations with a specified capacity.
• Implement a doubly linked list to keep track of the order of keys based on their usage.

• Use a hashmap to store key-value pairs for quick access and updates.

• When a key is accessed or updated, move it to the front of the linked list to mark it as the most recently used.

• When the cache reaches...read more
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Q2. 
Maximum of All Subarrays of Size K
Given an array of non-negative integers and an integer K representing the length of a subarray, your task is to determine the maximum elements for each subarray of size ...read more
Ans. 
Find the maximum elements for each subarray of size K in a given array.
• Iterate through the array and maintain a deque to store the indices of elements in decreasing order.

• Pop elements from the deque that are out of the current window.

• Keep track of the maximum element in each subarray of size K.

• Return the maximum elements for each subarray.
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Q3. What is virtual memory?
Ans. 
Virtual memory is a memory management technique that allows a computer to compensate for physical memory shortages by temporarily transferring data from RAM to disk storage.
• Virtual memory allows programs to use more memory than is physically available on the system.

• It helps in multitasking by allowing multiple programs to run simultaneously without running out of memory.

• Virtual memory uses a combination of RAM and disk...read more
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Q1. Trapping rainwater problem
Ans. 
Trapping rainwater problem
• The problem involves calculating the amount of rainwater that can be trapped between bars in an elevation map

• Use two pointers approach to calculate the water trapped at each bar

• Keep track of the maximum height on the left and right of each bar to calculate the trapped water
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Q1. Serach in sorted n*n matrix
Ans. 
Search for a target value in a sorted n*n matrix.
• Start from the top-right corner or bottom-left corner of the matrix.

• Compare the target value with the current element and move left or down accordingly.

• Repeat until the target value is found or the boundaries of the matrix are crossed.
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Q2. Maximum product subarray
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Q1. Iterative binary tree traversal
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Q2. Create BST from incoming stream of nodes
Ans. 
Create a Binary Search Tree (BST) from an incoming stream of nodes.
• Start with an empty BST

• For each incoming node, compare it with the root node and insert it accordingly

• Repeat the process until all nodes are inserted
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Q1. How do you Structure Database? Make Design ?
Ans. 
A well-structured database design is crucial for efficient data management.
• Identify entities and their relationships

• Normalize data to reduce redundancy

• Choose appropriate data types and constraints

• Consider performance and scalability

• Document the design and update as needed
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Q2. Ask about Low Level Design?
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Round duration - 40 minutes
Round difficulty - Easy

Timing: 12PM
Due to covid, the interviews happened over a video call on Zoom. They also shared an IDE link where we could write our code and the interview could see it.
The interviewer was very polite and helpful. She dropped hints in between to help me reach the final solution when I was stuck or needed some clarity. She wanted to check how analytically I could solve the problem. She focused more on my approaches towards the problem.
There was also a brief discussion on my resume and projects.

Q1. 
Serialization and Deserialization of an N-ary Tree
Given an N-ary tree where each node has at most 'N' child nodes, the task is to serialize the tree into a sequence of bits and then deserialize it back t...read more
Ans. 
Serialization and deserialization of an N-ary tree involves converting the tree into a sequence of bits and reconstructing the original tree from this format.
• Serialize the N-ary tree by traversing it in level order and representing each node and its children using a space-separated sequence of integers.

• Deserialize the serialized tree by parsing the input sequence and reconstructing the tree structure based on the provi...read more
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Round duration - 40 minutes
Round difficulty - Medium

Timing: Mid-afternoon
Due to covid, the interviews happened over a video call on Zoom. They also shared an IDE link where we could write our code and the interview could see it.
The interviewer was very polite and helpful. He dropped hints in between to help me reach the final solution when I was stuck or needed some clarity. He wanted to check how analytically I could solve the problem. He focused more on my approaches towards the problem.
There was also a brief discussion on my resume and projects.

Q1. 
Design a Constant Time Data Structure
Create a data structure that maintains mappings between keys and values, supporting the following operations in constant time:
1. INSERT(key, value): Add or update t...read more
Ans. 
Design a constant time data structure for key-value mappings with operations like INSERT, DELETE, SEARCH, GET, GET_SIZE, and IS_EMPTY.
• Use a hash table to achieve constant time complexity for operations.

• Implement INSERT, DELETE, SEARCH, GET, GET_SIZE, and IS_EMPTY functions.

• Ensure key is a string and value is a positive integer.

• Return appropriate results based on the operation type.

• Handle edge cases like key not found o
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Round duration - 30 Minutes
Round difficulty - Medium

Timing: Evening
Due to covid, the interviews happened over a video call on Zoom. They also shared an IDE link where we could write our code and the interview could see it.
There was a panel of three people as interviewers in this round.
I was also asked one behaviour questions in this round.

Q1. 
Simplify Directory Path Problem Statement
You are provided with a directory path in Unix-style notation, and your task is to simplify it according to given rules.
In a Unix-style file system:
• A dot (...read more
Ans. 
Given a Unix-style directory path, simplify it by following certain rules and return the simplified path.
• Use a stack to keep track of directories while iterating through the input path.

• Handle cases for '.', '..', and multiple slashes appropriately.

• Return the simplified path by joining the directories in the stack with '/' separator.
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