RedBus IOS Developer Interview Questions and Answers

Round duration - 65 minutes
Round difficulty - Easy

There were 2 sections – 
Aptitude and Logical Reasoning and MCQ based on Java question ,C++, coding for 20 min and 45 min respectively.
Section A- Not very difficult to clear this round although less time was a problem.
Section B- It contains 15 multiple choice question on c/c++,java and 4 simple coding questions

Q1. 
Cycle Detection in a Singly Linked List
Determine if a given singly linked list of integers forms a cycle or not.
A cycle in a linked list occurs when a node's next points back to a previous node in the ...read more
Ans. 
Detect if a singly linked list forms a cycle by checking if a node's next pointer points back to a previous node.
• Traverse the linked list using two pointers, one moving at double the speed of the other.

• If the two pointers meet at any point, there is a cycle in the linked list.

• Use Floyd's Cycle Detection Algorithm for O(N) time complexity and O(1) space complexity.
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Round duration - 75 minutes
Round difficulty - Medium

It was an online coding test in which 3 coding question were given.

Q1. 
Smallest Window Problem Statement
Given two strings, S and X, your task is to find the smallest substring in S that contains all the characters present in X.
Example:
Input:
S = "abdd", X = "bd"
Outpu...read more
Ans. 
Find the smallest substring in string S that contains all characters in string X.
• Iterate through string S and keep track of characters in X found in a window

• Use two pointers to maintain the window and slide it to find the smallest window

• Return the smallest window containing all characters in X
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Q2. 
Smallest Integer Not Representable as Subset Sum
Given a non-decreasing sorted array ARR of N positive numbers, determine the smallest positive integer that cannot be expressed as the sum of elements from...read more
Ans. 
Find the smallest positive integer that cannot be expressed as the sum of elements from any proper subset of a non-decreasing sorted array of positive numbers.
• Start with the smallest possible integer that cannot be represented, which is 1.

• Iterate through the array and update the smallest integer that cannot be represented.

• If the current element is greater than the smallest integer that cannot be represented, return tha...read more
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Q3. 
Minimum Steps for a Knight to Reach Target
Given a square chessboard of size 'N x N', determine the minimum number of moves a Knight requires to reach a specified target position from its initial position...read more
Ans. 
Calculate the minimum number of moves a Knight needs to reach a target position on a chessboard.
• Implement a function that takes knight's starting position, target position, and chessboard size as input

• Use breadth-first search algorithm to find the shortest path for the Knight

• Consider all possible 8 movements of the Knight on the chessboard

• Return the minimum number of moves required for the Knight to reach the target po
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Round duration - 60 minutes
Round difficulty - Easy

It started with a discussion on the programs given in coding round. They asked me about my interest field after that they directly jumped into Networking, Linux and Ethical Hacking part looking my interest domain. They asked me various question on networking and linux.
Then they asked me to code a simple c program

Q1. 
Reverse Linked List Problem Statement
Given a singly linked list of integers, return the head of the reversed linked list.
Example:
Initial linked list: 1 -> 2 -> 3 -> 4 -> NULL
Reversed link...read more
Ans. 
Reverse a singly linked list of integers and return the head of the reversed linked list.
• Iterate through the linked list and reverse the pointers to point to the previous node.

• Keep track of the current, previous, and next nodes while reversing the linked list.

• Update the head of the reversed linked list as the last node encountered during reversal.
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Q2. What are the port numbers of protocols such as FTP and SMTP?
Ans. 
FTP uses port number 21 and SMTP uses port number 25.
• FTP uses port 21 for data transfer and port 20 for control information.

• SMTP uses port 25 for email communication.

• Understanding port numbers is important for network communication.
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Q3. Can you explain the OSI Model?
Ans. 
The OSI Model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven layers.
• The OSI Model stands for Open Systems Interconnection Model.

• It consists of seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

• Each layer has specific functions and communicates with the adjacent layers.

• Example: Layer 1 (Physical) deals with physi...read more
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Q4. How do you copy files in Linux?
Ans. 
To copy files in Linux, you can use the 'cp' command.
• Use the 'cp' command followed by the source file and destination directory to copy a file.

• To copy a directory and its contents, use the '-r' flag with the 'cp' command.

• You can also use wildcards like '*' to copy multiple files at once.
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Round duration - 60 minutes
Round difficulty - Easy

Technical round with 3 problems based on DSA and Algorithms.

Q1. 
Smallest Integer Not Representable as Subset Sum
Given a non-decreasing sorted array ARR of N positive numbers, determine the smallest positive integer that cannot be expressed as the sum of elements from...read more
Ans. 
Find the smallest positive integer that cannot be expressed as the sum of elements from any proper subset of a given array.
• Sort the array in non-decreasing order.

• Iterate through the array and keep track of the smallest sum that can be formed.

• If the next element in the array is greater than the current sum + 1, then the answer is the current sum + 1.

• Return the answer as the smallest integer not representable as a subset
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Q2. 
Reverse Linked List Problem Statement
Given a singly linked list of integers, return the head of the reversed linked list.
Example:
Initial linked list: 1 -> 2 -> 3 -> 4 -> NULL
Reversed link...read more
Ans. 
Reverse a singly linked list of integers and return the head of the reversed linked list.
• Iterate through the linked list and reverse the pointers to point to the previous node instead of the next node.

• Use three pointers to keep track of the current, previous, and next nodes while reversing the linked list.

• Update the head of the reversed linked list to be the last node encountered during the reversal process.
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Q3. 
Smallest Window Problem Statement
Given two strings S and X containing random characters, the task is to find the smallest substring in S which contains all the characters present in X.
Input:
The first...read more
Ans. 
The task is to find the smallest substring in string S which contains all the characters present in string X.
• Iterate through string S and keep track of characters in X using a hashmap

• Use two pointers to maintain a sliding window and find the smallest window containing all characters in X

• Return the smallest window found
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Round duration - 60 minutes
Round difficulty - Easy

Technical round with questions based on OOPS and Angular.

Q1. What are the different OOP concepts?
Ans. 
OOP concepts include inheritance, encapsulation, polymorphism, and abstraction.
• Inheritance allows a class to inherit properties and behavior from another class.

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

• Polymorphism allows objects to be treated as instances of their parent class.

• Abstraction hides the complex implementation details of an object and only shows the necessar
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Round duration - 60 minutes
Round difficulty - Easy

Questions based on System Design, ajax, jquery were asked.

Q1. How would you design a traffic light system?
Ans. 
Designing a traffic light system involves creating a system that controls the flow of traffic at intersections.
• Divide the traffic light system into three main lights: red, yellow, and green.

• Implement timers to control the duration of each light.

• Include sensors to detect the presence of vehicles and pedestrians.

• Consider implementing a pedestrian crossing signal.

• Integrate a central control system to coordinate the timing
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Q2. How does AJAX work?
Ans. 
AJAX allows for asynchronous communication between client and server without needing to reload the entire page.
• AJAX stands for Asynchronous JavaScript and XML.

• It allows for sending and receiving data from a server without reloading the entire page.

• AJAX uses XMLHttpRequest object to make requests to the server.

• It can update parts of a web page without requiring a full page reload.

• Commonly used in web applications to pro
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Q3. What is the difference between AngularJS and jQuery?
Ans. 
AngularJS is a full-fledged MVC framework for building dynamic web applications, while jQuery is a lightweight library for DOM manipulation and event handling.
• AngularJS is a full-fledged MVC framework, providing features like two-way data binding, dependency injection, and routing.

• jQuery is a lightweight library primarily used for DOM manipulation and event handling.

• AngularJS is suitable for building single-page applic...read more
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Round duration - 90 minutes
Round difficulty - Medium

Coding question of medium level difficulty, from DP. 
18 MCQs were core CSE related concepts e.g: OS, OOPs, DBMS, Networking
Time was 90 minutes.

Q1. 
Minimum Cost to Destination
You are given an NxM matrix consisting of '0's and '1's. A '1' signifies that the cell is accessible, whereas a '0' indicates that the cell is blocked. Your task is to compute ...read more
Ans. 
Find the minimum cost to reach a destination in a matrix with blocked cells.
• Use Breadth First Search (BFS) algorithm to explore all possible paths from the starting point to the destination.

• Keep track of the cost incurred at each cell and update it as you move through the matrix.

• Return the minimum cost to reach the destination or -1 if it is unreachable.
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Round duration - 30 minutes
Round difficulty - Medium

It was an one-to-one interview. It checks your problem solving ability and a few OOPs, OS, DBMS etc concepts. Coding questions were related to array, queue and DP.

Q1. 
Triangle Formation Using Array Elements
Given an integer array/list ARR of length 'N', determine if it is possible to form at least one non-degenerate triangle using the values of the array as the sides o...read more
Ans. 
Determine if it is possible to form a non-degenerate triangle using array elements as sides.
• Check if the sum of any two sides is greater than the third side for all combinations of sides.

• If the above condition is met for any combination, return true; otherwise, return false.
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Q2. 
Maximum Sum of Non-Adjacent Elements
You are given an array/list of integers. The task is to return the maximum sum of a subsequence such that no two elements in the subsequence are adjacent in the given ...read more
Ans. 
Find the maximum sum of non-adjacent elements in an array.
• Use dynamic programming to keep track of the maximum sum at each index, considering whether to include the current element or not.

• At each index, the maximum sum can be either the sum excluding the current element or the sum including the current element but excluding the previous element.

• Iterate through the array and update the maximum sum accordingly.

• Example: F...read more
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Round duration - 45 minutes
Round difficulty - Easy

It was also a problem solving round. However after coding questions, they also asked CSE conceptual questions.

Q1. 
Sum Tree Conversion
Convert a given binary tree into its sum tree. In a sum tree, every node's value is replaced with the sum of its immediate children's values. Leaf nodes are set to 0. Finally, return th...read more
Ans. 
Convert a binary tree into a sum tree by replacing each node's value with the sum of its children's values. Return preorder traversal.
• Traverse the tree in a bottom-up manner, starting from the leaf nodes.

• For each node, update its value to the sum of its children's values.

• Set leaf nodes to 0.

• Return the preorder traversal of the modified tree.
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Q2. What are the core concepts of indexing in Database Management Systems (DBMS)?
Ans. 
Core concepts of indexing in DBMS include types of indexes, benefits of indexing, and factors affecting index performance.
• Types of indexes: B-tree, Hash, Bitmap, etc.

• Benefits of indexing: Faster data retrieval, improved query performance, reduced disk I/O.

• Factors affecting index performance: Selectivity, clustering factor, index fragmentation.

• Examples: Creating an index on a column in a table to speed up search queries
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