Uplers Senior Software Engineer Interview Questions and Answers

Q1. Hiring manager round
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Q2. Questions on previous projects
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Q1. Longest subsequence with sum zero
Ans. 
Find the longest subsequence in an array with sum zero.
• Iterate through the array and keep track of the running sum.

• Store the running sum in a hashmap along with the index.

• If the same sum is encountered again, the subsequence between the two indices has a sum of zero.
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Q2. Find diameter of tree
Ans. 
The diameter of a tree is the longest path between two leaf nodes in the tree.
• Calculate the longest path between two leaf nodes in the tree

• This can be done by finding the height of the left and right subtrees and adding them together

• The diameter of the tree is the maximum of either the diameter of the left subtree, the diameter of the right subtree, or the sum of the heights of the left and right subtrees
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Q1. System design: Hotel booking system
Ans. 
Design a hotel booking system for managing reservations and availability.
• Use a database to store hotel information, room availability, and reservations.

• Implement user authentication and authorization for booking.

• Include a search feature for users to find available rooms based on their criteria.

• Allow users to make reservations, modify or cancel them.

• Send confirmation emails to users after successful bookings.
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Divide one big integer by another

45 min round. Similar to Leetcode medium level question.

45 min coding round, 2 question asked

Q1. System design of proximity service
Ans. 
Design a system for proximity service
• Utilize geolocation data to track user locations

• Implement algorithms to calculate proximity between users

• Use real-time updates to notify users of nearby contacts
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Q1. Behavioral questions
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Q1. Minimum Knight Moves (LC Medium)
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Q2. OS, CN, DB concepts like multithreading, semaphore, tcp vs udp, transaction and ACId properties. Java concepts like stack vs heap(memory), error vs exception. Any 1 Project discussion for 10 mins
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Q1. Given array of integer create subarray with sum = 0
Ans. 
Create subarrays with sum = 0 from given array of integers.
• Iterate through the array and keep track of the running sum.

• Store the running sum in a hashmap and check if the current sum - any previous sum equals 0.

• If yes, then the subarray between those two indices has a sum of 0.
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Q2. Left view of binary tree
Ans. 
The left view of a binary tree is the set of nodes visible when the tree is viewed from the left side.
• Traverse the tree in a level order manner and keep track of the first node at each level.

• Use a queue to store nodes at each level and update the left view nodes accordingly.

• Example: For a binary tree with root node 1, left child 2, and right child 3, the left view would be [1, 2].
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Solve sudoku, row and columns should have 1-9 numbers and the numbers shouldnt repeat

Q1. What is the toughest problem you solved and once I answered they started digging in to it
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Q1. System Design - Design a parking lot
Ans. 
Design a parking lot system with features like parking, retrieving, and tracking available spots.
• Create a ParkingLot class with attributes like total number of spots, available spots, and a list of parked vehicles.

• Implement methods for parking a vehicle, retrieving a vehicle, and tracking available spots.

• Use data structures like arrays or lists to manage parked vehicles and available spots.

• Consider implementing feature...read more
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Q1. Several questions related to behavioral and troubleshooting
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Implement boolean canConstruct(String targetString, String[] dict) which returns true if we can construct the targetString by concatenating the words given in the dictionary

Q1. Implement key value store
Ans. 
Implement a key value store for storing and retrieving data efficiently.
• Use a hash table or a balanced tree data structure to store key-value pairs.

• Implement functions for inserting, updating, deleting, and retrieving key-value pairs.

• Consider implementing features like transactions, concurrency control, and data persistence.

• Example: Implement a simple key value store using a hash table in Python.
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Round duration - 60 minutes
Round difficulty - Medium

Technical Interview round with questions on C#, Design patterns, OOPS etc.

Q1. What is a base class?
Ans. 
A base class is a class that is used as a starting point for creating other classes. It can be inherited by other classes.
• Base class provides common attributes and methods that can be inherited by other classes

• Derived classes can extend or override the functionality of the base class

• Example: Animal can be a base class with attributes like name and methods like eat, sleep
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Q2. What is a singleton design pattern?
Ans. 
Singleton design pattern ensures a class has only one instance and provides a global point of access to it.
• Used to restrict the instantiation of a class to one object

• Commonly used in logging, caching, thread pools, database connections

• Implemented by creating a static instance of the class and a private constructor to prevent external instantiation
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Q3. What are the different access modifiers in C#?
Ans. 
Access modifiers in C# control the visibility and accessibility of classes, methods, and other members.
• Public - accessible from any other class or assembly

• Private - accessible only within the same class

• Protected - accessible within the same class or derived classes

• Internal - accessible within the same assembly

• Protected Internal - accessible within the same assembly or derived classes
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Q4. What is the default access modifier in C#?
Ans. 
The default access modifier in C# is 'private'.
• Default access modifier is applied if no access modifier is specified for a class member

• It restricts the access to the member within the same class

• Example: private int myVariable = 10;
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