Freecharge Backend Developer Interview Questions and Answers

Round duration - 90 minutes
Round difficulty - Easy

Nice environment

Q1. 
Zigzag Traversal of Binary Tree
Given a binary tree with integer values in its nodes, your task is to print the zigzag traversal of the tree.
Note:
In zigzag order, level 1 is printed from left to right...read more
Ans. 
Implement a function to print the zigzag traversal of a binary tree.
• Traverse the tree level by level, alternating the direction of traversal for each level.

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

• Print the nodes in zigzag order as per the given pattern.
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Round duration - 90 minutes
Round difficulty - Medium

Nice Environment

Q1. 
Prime Numbers Identification
Given a positive integer N, your task is to identify all prime numbers less than or equal to N.
Explanation:
A prime number is a natural number greater than 1 that has no po...read more
Ans. 
Identify all prime numbers less than or equal to a given positive integer N.
• Iterate from 2 to N and check if each number is prime

• Use the Sieve of Eratosthenes algorithm for better efficiency

• Optimize by only checking up to the square root of N for divisors
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Q2. What was the use of DBMS in your project, and how did you handle the problems that arose?
Ans. 
DBMS was used to store and manage data in the project, handled problems by optimizing queries and database design.
• Used DBMS to store and manage project data efficiently

• Optimized queries for better performance

• Designed database schema to handle data effectively

• Resolved concurrency issues by implementing proper locking mechanisms
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Round duration - 90 minutes
Round difficulty - Hard

Timing was 9 PM. Platform was not good. Platform was very lagging so overall it was bad experience.

Q1. 
Find the Third Greatest Element
Given an array 'ARR' of 'N' distinct integers, determine the third largest element in the array.
Input:
The first line contains a single integer 'T' representing the numb...read more
Ans. 
Find the third largest element in an array of distinct integers.
• Sort the array in descending order and return the element at index 2.

• Handle cases where the array has less than 3 elements separately.

• Consider using a set to ensure distinct elements in the array.
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Q2. 
Longest Palindromic Substring Problem Statement
You are provided with a string STR of length N. The goal is to identify the longest palindromic substring within this string. In cases where multiple palind...read more
Ans. 
Identify the longest palindromic substring in a given string.
• Iterate through the string and expand around each character to find palindromes

• Keep track of the longest palindrome found

• Return the longest palindromic substring with the smallest start index
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Q3. 
Ninja and Geometry Problem Statement
In this problem, Ninja is provided with two lines on a 2D plane. The first line 'AB' is determined by two points A and B. The second line 'PQ' is determined by two poi...read more
Ans. 
Calculate the intersection point of two lines on a 2D plane with precision up to six decimal places.
• Use the formula for finding the intersection point of two lines in 2D space.

• Handle precision issues that may arise due to floating-point arithmetic.

• Return -1.000000 -1.000000 if the lines do not intersect.

• Ensure the lines 'AB' and 'PQ' are distinct.
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Round duration - 90 minutes
Round difficulty - Medium

Timing was 9 PM. Platform was not good. Platform was very lagging so overall it was bad experience.

Q1. 
Find the Third Greatest Element
Given an array 'ARR' of 'N' distinct integers, determine the third largest element in the array.
Input:
The first line contains a single integer 'T' representing the numb...read more
Ans. 
Find the third largest element in an array of distinct integers.
• Sort the array in descending order and return the element at index 2.

• Handle cases where the array has less than 3 elements separately.

• Use a set to store distinct elements for efficient processing.
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Q2. 
Longest Palindromic Substring Problem Statement
You are provided with a string STR of length N. The task is to find the longest palindromic substring within STR. If there are several palindromic substring...read more
Ans. 
Find the longest palindromic substring in a given string.
• Iterate through the string and expand around each character to find palindromes

• Keep track of the longest palindrome found so far

• Return the longest palindromic substring
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Q3. 
Ninja and Geometry Problem Statement
In this problem, Ninja is provided with two lines on a 2D plane. The first line 'AB' is determined by two points A and B. The second line 'PQ' is determined by two poi...read more
Ans. 
Calculate the intersection point of two lines on a 2D plane with precision up to six decimal places.
• Implement a function to calculate the intersection point of two lines on a 2D plane

• Handle precision up to six decimal places in the output

• Return -1.000000 -1.000000 if the lines do not intersect

• Ensure the lines 'AB' and 'PQ' are distinct
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Round duration - 90 minutes
Round difficulty - Medium

Timing was 9 PM. Platform was not good. Platform was very lagging so overall it was bad experience.

Q1. 
Find the Third Greatest Element
Given an array 'ARR' of 'N' distinct integers, determine the third largest element in the array.
Input:
The first line contains a single integer 'T' representing the numb...read more
Ans. 
Find the third largest element in an array of distinct integers.
• Sort the array in descending order and return the element at index 2.

• Handle cases where there are less than 3 elements in the array.

• Consider edge cases like negative integers and duplicates.
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Q2. 
Longest Palindromic Substring Problem Statement
You are provided with a string STR of length N. The goal is to identify the longest palindromic substring within this string. In cases where multiple palind...read more
Ans. 
Identify the longest palindromic substring in a given string.
• Iterate through each character in the string and expand around it to find palindromes

• Keep track of the longest palindrome found so far

• Return the longest palindromic substring with the smallest start index
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Q3. 
Ninja and Geometry Problem Statement
In this problem, Ninja is provided with two lines on a 2D plane. The first line 'AB' is determined by two points A and B. The second line 'PQ' is determined by two poi...read more
Ans. 
Calculate the intersection point of two lines on a 2D plane with precision up to six decimal places.
• Implement a function to calculate the intersection point of two lines on a 2D plane

• Handle precision up to six decimal places in the output

• Return -1.000000 -1.000000 if the lines do not intersect

• Ensure the lines 'AB' and 'PQ' are distinct
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Round duration - 50 mins
Round difficulty - Medium

First round was coding round, where i was asked 2 DS algo questions, 1 was easy and other was of medium difficulty

Q1. 
Shortest Path in a Binary Matrix Problem Statement
Given a binary matrix of size N * M where each element is either 0 or 1, find the shortest path from a source cell to a destination cell, consisting only...read more
Ans. 
Find the shortest path in a binary matrix from a source cell to a destination cell consisting only of 1s.
• Use Breadth First Search (BFS) algorithm to find the shortest path.

• Keep track of visited cells to avoid revisiting them.

• Update the path length as you traverse through the matrix.

• Return -1 if no valid path exists.
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Round duration - 50 mins
Round difficulty - Easy

I was asked to design url shortner

Q1. Can you explain how you would design a URL shortener?
Ans. 
Design a URL shortener system
• Generate a unique short code for each URL

• Store the mapping of short code to original URL in a database

• Redirect users from short URL to original URL when accessed

• Consider implementing features like custom short codes, expiration dates, and analytics

• Ensure scalability and performance by using distributed systems and caching
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Round duration - 50 mins
Round difficulty - Medium

This was hiring manager round

Q1. Can you discuss a coding problem you encountered, your past projects, and any behavioral questions related to your experiences?
Ans. 
Discussed coding problem, past projects, and behavioral questions in SDE - 1 interview.
• Coding problem: Discussed how I optimized a sorting algorithm in a previous project.

• Past projects: Talked about a web application I developed using React and Node.js.

• Behavioral questions: Shared how I handled a conflict within a team during a project.

• Example: Explained how I implemented a feature in a mobile app that improved user en
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Q1. 1 - Easy Medium Question. Discuss the approach with interviewer and then implement it. The code should work, thats important.
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Q1. LLD round to design Chess.
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Q1. Hiring manager round. Grilling on resume and past experience questions
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Medium level leet code questions

Q1. Low Leven system design of Instagram.
Ans. 
Low level system design of Instagram involves designing the core components like database, storage, caching, and networking.
• Use sharding to distribute data across multiple database servers for scalability.

• Implement a caching layer using Redis or Memcached to improve performance.

• Utilize a content delivery network (CDN) for faster content delivery to users.

• Design a fault-tolerant storage system to ensure data durability ...read more
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Q1. Creating a high level design of a message queue system
Ans. 
Designing a message queue system for efficient communication between components
• Define the requirements and constraints of the system

• Choose a suitable messaging protocol (e.g. AMQP, MQTT)

• Design the message format and structure

• Implement mechanisms for message persistence and delivery guarantees

• Consider scalability and fault tolerance

• Use appropriate data structures and algorithms for efficient message handling
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Q1. What are your goals ?
Ans. 
My goal is to continuously improve my technical skills, contribute to impactful projects, and eventually move into a leadership role.
• Continuously improve technical skills through learning new technologies and best practices

• Contribute to impactful projects by delivering high-quality code and solutions

• Work towards moving into a leadership role by taking on more responsibilities and mentoring junior team members
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Q2. Why you choose jupiter
Ans. 
I chose Jupiter because of its strong gravitational pull and potential for scientific exploration.
• Jupiter's large size and mass make it a key player in shaping the solar system

• Its strong magnetic field and radiation belts provide valuable insights for space research

• Jupiter's moons, like Europa and Io, offer unique environments for potential exploration missions
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