SquadStack Product Engineer Interview Questions and Answers

Round duration - 15 minutes
Round difficulty - Easy

They called around afternoon to know more about me. It happened over a phone call. Don't lie about anything as they do some screening. Asked reason for change.

Round duration - 150 minutes
Round difficulty - Medium

Asked 5 coding questions on DSA. Total marks were 250. Each question has a different weightage. They give you around a week to complete the round.

Q1. 
Left View of a Binary Tree
Given a binary tree, your task is to print the left view of the tree. The left view of a binary tree contains the nodes visible when the tree is viewed from the left side.
Inpu...read more
Ans. 
The task is to print the left view of a binary tree, which contains the nodes visible when viewed from the left side.
• Traverse the binary tree level by level and keep track of the leftmost node at each level.

• Use a queue for level order traversal and maintain a count of nodes at each level.

• Print the leftmost node at each level to get the left view of the binary tree.
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Q2. 
Find Duplicates in an Array
Given an array ARR of size 'N', where each integer is in the range from 0 to N - 1, identify all elements that appear more than once.
Return the duplicate elements in any orde...read more
Ans. 
Identify duplicate elements in an array of integers within a specified range.
• Iterate through the array and keep track of the frequency of each element using a hashmap.

• Return elements with frequency greater than 1 as duplicates.

• Handle edge cases such as empty array or no duplicates found.

• Example: For input [0, 3, 1, 2, 3], output should be [3].
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Q3. 
Maximum Subarray Sum Problem Statement
Given an array of integers, determine the maximum possible sum of any contiguous subarray within the array.
Example:
Input:
array = [34, -50, 42, 14, -5, 86]
Out...read more
Ans. 
Find the maximum sum of any contiguous subarray within an array of integers.
• Iterate through the array and keep track of the maximum sum of subarrays encountered so far.

• At each index, decide whether to include the current element in the subarray or start a new subarray.

• Update the maximum sum if a new maximum is found.

• Time complexity should be O(N) to iterate through the array once.

• Example: For array [34, -50, 42, 14, -5...read more
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Q4. 
Longest Common Subsequence Problem Statement
Given two strings STR1 and STR2, determine the length of their longest common subsequence.
A subsequence is a sequence that can be derived from another sequen...read more
Ans. 
The task is to find the length of the longest common subsequence between two given strings.
• Implement a function to find the longest common subsequence between two strings.

• Use dynamic programming to solve this problem efficiently.

• Iterate through the strings and build a matrix to store the lengths of common subsequences.

• Return the length of the longest common subsequence found.
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Q5. 
Reverse Words in a String: Problem Statement
You are given a string of length N. Your task is to reverse the string word by word. The input may contain multiple spaces between words and may have leading o...read more
Ans. 
Reverse words in a string word by word, removing leading/trailing spaces and extra spaces between words.
• Split the input string by spaces to get individual words

• Reverse the order of the words

• Join the reversed words with a single space in between

• Remove any leading or trailing spaces
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Round duration - 20 minutes
Round difficulty - Easy

Asks questions about your experience. Gives introduction to the role and what you'll be doing. Ask any questions about the company, culture or job.

Round duration - 120 minutes
Round difficulty - Medium

Q1. How would you design a parking lot system?
Ans. 
Designing a parking lot system involves layout planning, ticketing system, payment methods, security measures, and efficient traffic flow.
• Layout planning to maximize space and accommodate different types of vehicles

• Implementing a ticketing system for entry and exit tracking

• Offering various payment methods such as cash, credit card, and mobile payments

• Installing security measures like CCTV cameras and automated gates

• Ens...read more
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Round duration - 60 minutes
Round difficulty - Easy

Asked technical questions around DBMS and Java.

Q1. What are the ACID properties in database management systems?
Ans. 
ACID properties are a set of properties that guarantee reliability and consistency in database transactions.
• Atomicity: Ensures that all operations in a transaction are completed successfully or none at all.

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

• Isolation: Ensures that the execution of multiple transactions concurrently does not interfere with each other.

• Dur...read more
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Q2. What is an Inner Join?
Ans. 
Inner Join is a type of SQL join that returns only the rows with matching values in both tables.
• Inner Join combines rows from two tables based on a related column between them

• It returns only the rows where there is a match between the columns in both tables

• Non-matching rows are not included in the result set
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Round duration - 60 minutes
Round difficulty - Easy

2 coding questions were asked in this round. It was easier than the previous online coding round.

Q1. 
Arithmetic Expression Evaluation Problem Statement
You are provided with a string expression consisting of characters '+', '-', '*', '/', '(', ')' and digits '0' to '9', representing an arithmetic express...read more
Ans. 
Evaluate arithmetic expressions in infix notation with given operators and precedence rules.
• Parse the infix expression to postfix using a stack and then evaluate the postfix expression using another stack

• Handle operators precedence and associativity while converting to postfix

• Use a stack to keep track of operands and operators during evaluation

• Ensure to handle parentheses properly to maintain correct order of operation...read more
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Q2. 
Covid Vaccination Distribution Problem
As the Government ramps up vaccination drives to combat the second wave of Covid-19, you are tasked with helping plan an effective vaccination schedule. Your goal is...read more
Ans. 
The task is to plan an effective vaccination schedule to maximize the number of vaccines administered on a particular day, while adhering to certain rules.
• Given 'n' days for vaccination drive, 'maxVaccines' available, and 'dayNumber' to maximize vaccines on.

• Distribute vaccines each day with a positive number, ensuring the difference between consecutive days is not more than 1.

• Output the maximum number of vaccines admin...read more
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Round duration - 60 minutes
Round difficulty - Medium

It was a bar raiser round where they ask system design questions mostly around APIs and Databases.
Asked to create APIs and design tables.

Round duration - 60 minutes
Round difficulty - Easy

Round with one of the founders to see for cultural fit. General questions about you, your journey, reason for change, priorities when looking for a job.

Round duration - 30 minutes
Round difficulty - Easy

The round was a resume walkthrough and one question related to DS as I mentioned one project related to that.

It happened in the morning. You should walkthrough your resume before going for this round.

Q1. Can you explain how you handled scalability in the project mentioned in your resume?
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Round duration - 60 minutes
Round difficulty - Medium

Round contained 1 DSA question

Q1. 
Factorial of a Number Problem Statement
You are provided with an integer 'N'. Your task is to calculate and print the factorial of 'N'. The factorial of a number 'N', denoted as N!, is the product of all ...read more
Ans. 
Calculate and print the factorial of a given integer 'N'.
• Iterate from 1 to N and multiply each number to calculate factorial

• Handle edge cases like N=0 or N=1 separately

• Use recursion or iterative approach to calculate factorial
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Round duration - 60 minutes
Round difficulty - Easy

A problem based on data and I had to find some interference from the same

Round duration - 60 minutes
Round difficulty - Easy

This was a culture fit round based on questions like why do you want to join a startup?
What do you expect working in a startup and how would you solve a challenge you are facing.
The career path that you are aiming