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
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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

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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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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React based
problem solving round

Asked medium level graph question.

Asked LLD question with at flow executable.

Q1. Asked HLD questions.
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Q1. Screening round: How do you add a new element to a complete binary tree, where all levels are fully populated except for the last level, which is filled from left to right?
Ans. 
To add an element to a complete binary tree, insert it at the next available position, maintaining the complete structure.
• 1. Identify the next available position in the tree, which is the leftmost empty spot at the last level.

• 2. Use a queue or array to keep track of nodes for level-order traversal to find the insertion point.

• 3. Insert the new element as a child of the last node in the queue or array.

• 4. If the last leve...read more
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Q2. Design a parking lot system that allows users to park and unpark their vehicles. Given a specific slot, the system should return the vehicle located in that slot. Additionally, what changes would be necess...read more
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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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