Toast Software Developer Interview Questions and Answers

Round duration - 60 minutes
Round difficulty - Medium

The interviewer was really cool. He realized that I mostly work on java applications so he chose to ask me stuff related to that. He didn't want me to know the answer well but just wanted me to approach to it, maybe think more. He went through my resume back and forth and asked mostly about all my projects and their logic and how could I take them to the next level.
Tips: Be confident. Its okay not to know any answer, just try giving it a shot in the approach.

Q1. What is the difference between an abstract class and an interface in Java?
Ans. 
Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.
• Abstract class can have constructors, member variables, and methods with implementation.

• Interface can only have abstract methods and constants.

• A class can implement multiple interfaces but can only extend one abstract class.

• Example: Abstract class - Animal with abstract method 'eat', Interface - Flyable with m...read more
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Q2. What is the difference between 'final', 'finally', and 'finalize' in Java?
Ans. 
final is a keyword used to declare constants, finally is a block used in exception handling, and finalize is a method used for cleanup.
• final is a keyword used to declare constants in Java, meaning the value cannot be changed once assigned. Example: final int x = 10;

• finally is a block used in exception handling to ensure a piece of code is always executed, whether an exception is thrown or not. Example: try { // code } ...read more
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Q3. What is the difference between the private and final access modifiers in Java?
Ans. 
Private restricts access to the class itself, while final prevents inheritance and method overriding.
• Private access modifier restricts access to the class itself, while final access modifier prevents inheritance and method overriding.

• Private members are only accessible within the same class, while final classes cannot be extended and final methods cannot be overridden.

• Example: private int num; - num can only be accesse...read more
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Q4. What are the steps for establishing a JDBC connection?
Ans. 
Establishing a JDBC connection involves loading the driver, creating a connection, creating a statement, executing queries, and handling exceptions.
• Load the JDBC driver using Class.forName() method

• Create a connection using DriverManager.getConnection() method

• Create a statement using connection.createStatement() method

• Execute queries using statement.executeQuery() method

• Handle exceptions using try-catch blocks
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Q5. What is JSON?
Ans. 
JSON is a lightweight data interchange format used to store and transmit data between a server and a web application.
• JSON stands for JavaScript Object Notation.

• It is easy for humans to read and write, and easy for machines to parse and generate.

• JSON is language-independent and can be used with any programming language.

• Example: {"name": "John", "age": 30}

• Example: [{"name": "Alice", "age": 25}, {"name": "Bob", "age": 35}...read more
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Q6. What do you know about garbage collection in Java?
Ans. 
Garbage collection in Java is the process of automatically managing memory by deallocating objects that are no longer needed.
• Garbage collection helps in preventing memory leaks by reclaiming memory used by objects that are no longer referenced.

• Java uses a garbage collector to automatically manage memory, unlike languages like C++ where memory management is manual.

• Garbage collection in Java can be triggered by calling S...read more
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Round duration - 30 minutes
Round difficulty - Easy

I wouldn't say it went great but it was fine. I did not think I would clear it as for most of the questions the interviewer seemed disappointed and wanted more out of me.

Round duration - 90 minutes
Round difficulty - Medium

Timing: 90 mins
Environment: Online coding round
No of questions: 3 Questions(225 marks) were asked.

Q1. 
Quick Sort Problem Statement
You are provided with an array of integers. The task is to sort the array in ascending order using the quick sort algorithm.
Quick sort is a divide-and-conquer algorithm. It ...read more
Ans. 
Yes, the quick sort algorithm can be enhanced to achieve NlogN complexity in the worst case by using randomized quick sort or median of three pivot selection.
• Use randomized quick sort to randomly select the pivot element, reducing the chances of worst-case scenarios.

• Implement median of three pivot selection to choose a pivot that is closer to the median value, improving partitioning efficiency.

• Consider using dual pivot...read more
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Q2. 
Find K'th Character of Decrypted String
You are given an encrypted string where repeated substrings are represented by the substring followed by its count. Your task is to find the K'th character of the d...read more
Ans. 
Given an encrypted string with repeated substrings represented by counts, find the K'th character of the decrypted string.
• Parse the encrypted string to extract substrings and their counts

• Iterate through the substrings and counts to build the decrypted string

• Track the position in the decrypted string to find the K'th character
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Q3. 
Weighted Job Scheduling Problem Statement
You have 'N' jobs, each with a start time, end time, and profit. Your task is to identify the maximum profit that can be earned by scheduling these jobs such that...read more
Ans. 
The Weighted Job Scheduling problem involves maximizing profit by scheduling non-overlapping jobs with given start times, end times, and profits.
• Sort the jobs by end time in ascending order.

• Initialize an array 'dp' to store maximum profit at each job index.

• For each job, find the latest non-overlapping job and update 'dp' with the maximum profit.

• Return the maximum profit from 'dp'.
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Round duration - 45 minutes
Round difficulty - Medium

Timing: evening
Environment: Virtual(remote)
Activity:
It was a resume screening + DSA round . There were 2 interviewers in this round. Initially , a brief introduction was given by them & later , they started with projects listed in my resume . They first asked me to explain about the projects , asked some questions related to its implementation & its actual use case in real world (where it can be used) .Later , they switched to DSA part , a total of 2 questions of easy medium difficulty level were asked . I only remember 1 question that was similar to Minimum platform problem.

After this , They asked me for favourite subjects. I said Operation Systems . Then , they asked for some concepts in OS , including CPU scheduling & its algos like Round robin , SJF etc and later asked which type of scheduling algorithm is used to design actual systems .

Q1. 
Minimum Number of Platforms Problem
Your task is to determine the minimum number of platforms required at a railway station so that no train has to wait.
Explanation:
Given two arrays:
• AT - represent...read more
Ans. 
Determine the minimum number of platforms needed at a railway station so that no train has to wait.
• Sort the arrival and departure times arrays in ascending order.

• Use two pointers to iterate through the arrays and keep track of the number of platforms needed.

• Increment the number of platforms needed when a train arrives and decrement it when a train departs.

• Return the maximum number of platforms needed at any point.

• Examp...read more
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Round duration - 50 minutes
Round difficulty - Medium

It was System design round.Though , it also started with a brief introduction & later , asked about projects . As my project was related to test classification . In that context , they asked me to design a low level Suggestion system(In any preferred language) .

Q1. 
Spell Checker Problem Statement
You are provided with a list of strings, DICTIONARY[], representing the correct spellings of words, and a query string QUERY that may contain misspelled words. Your task is...read more
Ans. 
Given a list of correct spellings and a query string, return a list of suggested correct spellings if the query is misspelled.
• Iterate through the dictionary to check for matching prefixes with the query string.

• If a match is found, add the corresponding word to the list of suggestions.

• Return the list of suggestions if the query is misspelled, otherwise return an empty list.
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Round duration - 75 minutes
Round difficulty - Hard

Coding Test with 3 problems. 1 Easy , 1 Medium , 1 Very Hard

Q1. 
Job Scheduling Problem
You are provided with a list of jobs, where each job has a specific deadline and profit. The goal is to schedule these jobs such that the total profit is maximized. Each job require...read more
Ans. 
The goal is to schedule jobs to maximize profit while meeting deadlines. Each job takes one unit of time and only one job can be scheduled at a time.
• Sort the jobs in decreasing order of profit

• Iterate through the sorted jobs and schedule them based on their deadlines

• Keep track of the total profit achieved

• Ensure each job is completed before its deadline
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Q2. 
Spiral Order Traversal of a Binary Tree
Given a binary tree with N nodes, your task is to output the Spiral Order traversal of the binary tree.
Input:
The input consists of a single line containing elem...read more
Ans. 
Implement a function to return the spiral order traversal of a binary tree.
• Traverse the binary tree level by level, alternating between left to right and right to left.

• Use a queue to keep track of nodes at each level.

• Append nodes to the result list in the order they are visited.
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Q3. 
Structurally Unique Binary Trees of Dragon Balls
Goku has ‘N’ Dragon Balls, where each Dragon Ball is unique. The ith Dragon Ball has ‘i’ stars on it, meaning the first Dragon Ball has 1 star, the second ...read more
Ans. 
Count the number of structurally unique binary trees that can be constructed with given Dragon Balls.
• Use dynamic programming to solve this problem efficiently.

• The number of structurally unique binary trees can be calculated using Catalan numbers.

• For each test case, calculate the number of structurally unique binary trees modulo 10^9 + 7.

• Return the count of unique binary trees for each test case.
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Round duration - 60 minutes
Round difficulty - Hard

In depth questions on Subjects like OOP , DBMS , OS , Javascript.

Round duration - 40 minutes
Round difficulty - Hard

Questions on my resume, projects, internship done. Interviewer was a bit harsh on me.

Q1. What are the differences between low-level and high-level programming languages, and can you explain some kernel-related questions?
Ans. 
Low-level languages interact directly with hardware, while high-level languages are more abstract and easier to read/write.
• Low-level languages are closer to machine code and hardware, while high-level languages are closer to human language.

• Low-level languages require more manual memory management and are less portable, while high-level languages have automatic memory management and are more portable.

• Examples of low-lev...read more
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Round duration - 90 Minutes
Round difficulty - Medium

It was an online technical round. There were around 20 MCQs and two coding questions. The round had an login window of 30 minutes. One coding question was of the level leetcode medium and the other was leetcode hard.

Q1. 
Search in a Row-wise and Column-wise Sorted Matrix Problem Statement
You are given an N * N matrix of integers where each row and each column is sorted in increasing order. Your task is to find the positi...read more
Ans. 
Given a sorted N * N matrix, find the position of a target integer X.
• Iterate over each row and column to search for the target integer

• Utilize the sorted nature of the matrix to optimize the search process

• Return the position of the target integer if found, else return -1 -1
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Q2. 
Euler’s Totient Function Problem Statement
Given an integer N, your task is to determine the count of integers between 1 and N (inclusive) that are coprime to N.
Input:
The first line contains an intege...read more
Ans. 
Euler's Totient Function calculates count of integers coprime to N between 1 and N.
• Implement Euler's Totient Function to calculate count of coprime integers to N.

• Use the formula: phi(N) = N * (1 - 1/p1) * (1 - 1/p2) * ... * (1 - 1/pk) where p1, p2, ..., pk are prime factors of N.

• Example: For N = 9, phi(9) = 9 * (1 - 1/3) = 6.
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Round duration - 60 Minutes
Round difficulty - Medium

It was a technical + HR round. The interview panel consisted of two technical guys and one person from HR.

Q1. 
Sort Array of Strings Problem Statement
Given an array of strings ARRSTR[] of size N, and a character C, your task is to sort the ARRSTR[] array according to a new alphabetical order that starts with the ...read more
Ans. 
Sort an array of strings based on a new alphabetical order starting with a given character.
• Iterate through the array of strings and compare each string with the given character to determine the new order.

• Implement a custom comparator function to sort the strings based on the new alphabetical order.

• Use built-in sorting functions in programming languages like Python, Java, or C++ to efficiently sort the array.
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Q2. Can you explain the pillars of Object-Oriented Programming (OOP)?
Ans. 
The pillars of OOP are Inheritance, Encapsulation, Abstraction, and Polymorphism.
• Inheritance allows a class to inherit properties and behavior from another class.

• Encapsulation restricts access to certain components of an object, protecting its integrity.

• Abstraction hides complex implementation details and only shows the necessary features.

• Polymorphism allows objects to be treated as instances of their parent class, ena...read more
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