ElasticRun Associate Software Engineer Interview Questions and Answers

Round duration - 120 minutes
Round difficulty - Medium

Due to pandemic placement process went virtual. Test was conducted at 10 A.M.

Q1. 
Decode String Problem Statement
Your task is to decode a given encoded string back to its original form.
Explanation:
An encoded string format is <count>[encoded_string], where the 'encoded_string...read more
Ans. 
The task is to decode an encoded string back to its original form by repeating the encoded string 'count' times.
• Parse the input string to extract the count and the encoded string within the brackets

• Use recursion to decode the encoded string by repeating it 'count' times

• Handle nested encoded strings by recursively decoding them

• Output the decoded string for each test case
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Q2. 
Detect and Remove Loop in Linked List
For a given singly linked list, identify if a loop exists and remove it, adjusting the linked list in place. Return the modified linked list.
Expected Complexity:
A...read more
Ans. 
Detect and remove loop in a singly linked list in place with O(n) time complexity and O(1) space complexity.
• Use Floyd's Cycle Detection Algorithm to identify the loop in the linked list.

• Once the loop is detected, use two pointers approach to find the start of the loop.

• Adjust the pointers to remove the loop and return the modified linked list.

• Example: For input 5 2 and 1 2 3 4 5, output should be 1 2 3 4 5.
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Q3. 
Infix to Postfix Conversion
You are provided with a string EXP which represents a valid infix expression. Your task is to convert this given infix expression into a postfix expression.
Explanation:
An i...read more
Ans. 
Convert a given infix expression to postfix expression.
• Use a stack to keep track of operators and operands.

• Follow the rules of precedence for operators (*, / have higher precedence than +, -).

• Handle parentheses by pushing them onto the stack and popping when closing parenthesis is encountered.
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Round duration - 30 minutes
Round difficulty - Medium

Due to pandemic placement process went virtual. Test was conducted at 2 P.M.

Q1. 
Find First Repeated Character in a String
Given a string 'STR' composed of lowercase English letters, identify the character that repeats first in terms of its initial occurrence.
Example:
Input:
STR =...read more
Ans. 
The task is to find the first repeated character in a given string of lowercase English letters.
• Iterate through the string and keep track of characters seen so far in a set.

• If a character is already in the set, return it as the first repeated character.

• If no repeated character is found, return '%'.
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Round duration - 45 minutes
Round difficulty - Medium

Video Call interview where the interview happened for around 45 minutes.

Q1. 
Maximum Sum Path in a Binary Tree Problem Statement
You are provided with a binary tree consisting of N nodes where each node has an integer value. The task is to determine the maximum sum achievable by a...read more
Ans. 
Find the maximum sum achievable by a simple path between any two nodes in a binary tree.
• Traverse the binary tree to find all possible paths and calculate their sums.

• Keep track of the maximum sum encountered during traversal.

• Consider paths that may include the same node twice.

• Implement a recursive function to explore all paths in the tree.

• Optimize the solution to avoid redundant calculations.
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Round duration - 30 minutes
Round difficulty - Easy

Video Call interview where the interview happened for around 30 minutes.

Round duration - 45 Minutes
Round difficulty - Medium

Q1. Design a class booking application for students.
Ans. 
A class booking application for students to schedule and manage their classes.
• Create a class booking system where students can view available classes, book classes, and manage their schedule.

• Include features like class search, class details, booking confirmation, and calendar view.

• Implement user authentication to ensure only registered students can book classes.

• Allow students to cancel or reschedule classes with proper...read more
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Round duration - 60 Minutes
Round difficulty - Medium

The interviewer understand the current problem statement I was working on. 
Asked the clarifying questions and alternative approaches to solve the same and their tradeoffs.
Also, asked about the technologies I was using in depth and reason for choosing the same.

Q1. 
Gas Tank Problem Statement
You have a car with a gas tank of infinite capacity. There are 'N' gas stations located along a circular route, numbered from 0 to N-1. You begin your journey with an empty tank...read more
Ans. 
Find the starting gas station index to complete a circular route with gas and cost arrays.
• Iterate through gas stations, keeping track of gas remaining after each station

• If gas remaining is negative, reset starting station to current station + 1

• If total gas remaining at the end is greater than or equal to total cost, return starting station index
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Round duration - 45 Minutes
Round difficulty - Medium

This round was their with the CTO and was mostly the culture fitment round.

Round duration - 30 Minutes
Round difficulty - Easy

This round was with the cofounder and was mostly culture fitment.

Q1. Jump Game - II
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Q2. Number of Island
Ans. 
Count the number of islands in a given grid of '1's and '0's.
• Iterate through the grid and for each '1' encountered, perform a depth-first search to mark all connected '1's as visited.

• Increment the island count for each new island encountered.

• Consider edge cases like grid boundaries and handling visited cells.
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