Eternal Limited Software Developer Intern Interview Questions and Answers

Round duration - 150 minutes
Round difficulty - Medium

The interview was scheduled at 6 pm and the duration of the interview was 1.5 hrs but went for around 2.5 hrs. The interviewer started with a brief intro about me. Asked me some coding questions. After coding questions he started asking questions on dbms like difference between sql and no sql, what is horizontal and vertical scaling and when we use them. Then some questions on computer networks like how web browsers works, different between http and HTTPS, what is TCP. After this he asked about my projects and the technology I worked on during the intern.

Q1. 
Snake and Ladder Problem Statement
Given a Snake and Ladder Board with 'N' rows and 'N' columns filled with numbers from 1 to N*N starting from the bottom left of the board, and alternating direction each...read more
Ans. 
Find the minimum number of dice throws required to reach the last cell on a Snake and Ladder board.
• Use Breadth First Search (BFS) algorithm to find the shortest path on the board.

• Create a mapping of each cell to its next possible moves based on dice outcomes.

• Consider the snakes and ladders on the board while calculating the next possible moves.

• Track the number of dice throws needed to reach each cell and update it as y...read more
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Q2. 
Deletion In Doubly Linked List
You are given a Doubly Linked List with 'N' positive integers. Your task is to delete a node at a given position 'POS' in this linked list.
Input:
The first line of input ...read more
Ans. 
Implement a function to delete a node at a given position in a Doubly Linked List.
• Traverse to the node at the specified position in the Doubly Linked List.

• Adjust the pointers of the previous and next nodes to remove the node at the specified position.

• Update the pointers accordingly to maintain the integrity of the Doubly Linked List.

• Handle edge cases such as deleting the head or tail node.

• Ensure to free the memory of t...read more
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Round duration - 20 minutes
Round difficulty - Easy

Round duration - 90 minutes
Round difficulty - Medium

The interview started in the evening on google meet. and extended for 90 minutes. The interviewer was very helpful and he shared a collaborative code editor to discuss several problems.

Q1. 
Find All Pairs Adding Up to Target
Given an array of integers ARR of length N and an integer Target, your task is to return all pairs of elements such that they add up to the Target.
Input:
The first line ...read more
Ans. 
Given an array of integers and a target, find all pairs of elements that add up to the target.
• Iterate through the array and for each element, check if the complement (target - current element) exists in a hash set.

• If the complement exists, add the pair to the result. If not, add the current element to the hash set.

• Handle cases where the same element is used twice in a pair by keeping track of the frequency of elements.

• ...read more
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Q2. 
Convert a Binary Tree to a Sum Tree
Given a binary tree of integers, convert the binary tree into a sum tree where each node's value is replaced by the sum of the values of its left and right subtrees in ...read more
Ans. 
Convert a binary tree into a sum tree where each node's value is replaced by the sum of its left and right subtrees.
• Traverse the tree in postorder fashion to calculate the sum of left and right subtrees for each node.

• Set leaf nodes to zero.

• Update the node values with the sum of left and right subtrees.
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Q3. 
LFU Cache Design Problem
Design and implement a Least Frequently Used (LFU) Cache with the following functionalities:
1. put(U__ID, value): Insert the value in the cache if the key ('U__ID') is not alrea...read more
Ans. 
Design and implement a Least Frequently Used (LFU) Cache with put and get functionalities, handling capacity and frequency of use.
• Implement a LFU cache with put and get functions

• Handle capacity and frequency of use for eviction

• Return the value of key if present, -1 otherwise

• Consider multiple elements with least frequency, remove least recently used

• Example: Insert, update, and retrieve values based on operations
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Q4. Write a SQL query to find the X percentile of students.
Ans. 
SQL query to find the X percentile of students
• Use the NTILE() function to divide students into X groups

• Calculate the total number of students and the number of students in each group

• Select the students from the group that corresponds to the X percentile
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Q5. Can you explain polymorphism and provide examples of real-time and run-time polymorphism?
Ans. 
Polymorphism is the ability of a function or method to behave differently based on the object it is called on.
• Polymorphism allows objects of different classes to be treated as objects of a common superclass.

• Real-time polymorphism is achieved through method overloading, where multiple methods have the same name but different parameters.

• Run-time polymorphism is achieved through method overriding, where a subclass provide...read more
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Round duration - 60 Minutes
Round difficulty - Easy

The overall interview experience was quite smooth and the interviewers were very kind.
I was asked 2 coding questions.

Q1. 
Reverse Doubly Linked List in Groups Problem
You are provided with a Doubly Linked List consisting of integers and a positive integer 'K', which represents the size of the group. Your task is to modify th...read more
Ans. 
Reverse groups of K nodes in a doubly linked list
• Iterate through the linked list in groups of size K

• Reverse each group of nodes

• Handle cases where the number of remaining nodes is less than K
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Q2. 
Largest Rectangle in Histogram Problem Statement
You are given an array/list HEIGHTS of length N, where each element represents the height of a histogram bar. The width of each bar is considered to be 1.
...read more
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Round duration - 50 Minutes
Round difficulty - Medium

3 coding questions were asked and 1 on system design.

Q1. 
Maximize the Sum Through Two Arrays
You are given two sorted arrays of distinct integers, ARR1 and ARR2. If there is a common element in both arrays, you can switch from one array to the other.
Your task...read more
Ans. 
Given two sorted arrays, find the path through common elements for maximum sum.
• Start with the array containing the smaller first common element

• Switch arrays at common elements to maximize the sum

• Continue adding elements until the end of the arrays
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Q2. 
Number of Islands Problem Statement
You are provided with a 2-dimensional matrix having N rows and M columns, containing only 1s (land) and 0s (water). Your goal is to determine the number of islands in t...read more
Ans. 
Count the number of islands in a 2D matrix of 1s and 0s.
• Use Depth First Search (DFS) or Breadth First Search (BFS) to traverse the matrix and identify connected groups of 1s.

• Maintain a visited array to keep track of visited cells to avoid redundant traversal.

• Increment the island count each time a new island is encountered.

• Consider all eight possible directions for connectivity between cells.

• Handle edge cases such as bo...read more
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Q3. How would you design Instagram?
Ans. 
Designing Instagram involves creating a user-friendly platform for sharing photos and videos with social networking features.
• Focus on a clean and intuitive user interface for easy navigation

• Implement features like photo filters, stories, direct messaging, and explore page

• Incorporate algorithms for personalized content recommendations

• Ensure robust security measures for user data protection

• Integrate advertising options f...read more
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Round duration - 15 Minutes
Round difficulty - Medium