Regenersis Interview Questions, Process, and Tips for Experienced

Round duration - 150 Minutes
Round difficulty - Medium

Have to attempt 2 programming questions within 2:30 hours. Can take any time over the weekend. Relatively easy problems. Questions were long, but the solution code was small.

Q1. 
The Skyline Problem
Compute the skyline of given rectangular buildings in a 2D city, eliminating hidden lines and forming the outer contour of the silhouette when viewed from a distance. Each building is ...read more
Ans. 
Compute the skyline of given rectangular buildings in a 2D city, eliminating hidden lines and forming the outer contour of the silhouette.
• Iterate through the buildings and create a list of critical points (x, y) where the height changes.

• Sort the critical points based on x-coordinate and process them to generate the skyline.

• Merge consecutive horizontal segments of equal height to ensure no duplicates in the output.
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Q2. 
MergeSort Linked List Problem Statement
You are given a Singly Linked List of integers. Your task is to sort the list using the 'Merge Sort' algorithm.
Input:
The input consists of a single line contain...read more
Ans. 
Sort a Singly Linked List using Merge Sort algorithm.
• Implement the Merge Sort algorithm for linked lists.

• Divide the list into two halves, sort each half recursively, then merge them.

• Use a fast and slow pointer to find the middle of the list for splitting.

• Handle the base case of a single node or empty list.

• Example: Input: 4 3 2 1 -1, Output: 1 2 3 4
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Round duration - 240 Minutes
Round difficulty - Medium

Had to solve 1 programming question in 4 hours. It was in the morning on a weekend. The environment was not so good. It was a small institute and got very crowded. The platform was also buggy. but the question was not difficult. Was able to solve it in just 1 hour and leave.

Q1. 
Batch Photography Problem
Alex has acquired a machine that can photocopy photos in batches of a minimum size 'K'. Given 'N' photos with resolutions represented in an integer array photos, the machine prod...read more
Ans. 
Minimize maximum error by splitting photos into batches of size at least 'K'.
• Sort the array of resolutions in ascending order.

• Iterate through the array and calculate the error for each possible batch.

• Return the minimum possible maximum error found.
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Round duration - 30 Minutes
Round difficulty - Easy

It was in the afternoon. The interviewer basically asked me what technologies I have worked on. Checked my knowledge of those technologies with simple questions. Told me what I'll be working on if I get selected.

Q1. 
Sort 0 1 2 Problem Statement
Given an integer array arr of size 'N' containing only 0s, 1s, and 2s, write an algorithm to sort the array.
Input:
The first line contains an integer 'T' representing the n...read more
Ans. 
Sort an integer array containing only 0s, 1s, and 2s in linear time complexity.
• Use three pointers to keep track of the positions of 0s, 1s, and 2s in the array.

• Iterate through the array and swap elements based on the values encountered.

• Maintain left pointer for 0s, right pointer for 2s, and current pointer for traversal.

• Example: If current element is 0, swap it with element at left pointer and increment both pointers.

• E...read more
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Round duration - 90 Minutes
Round difficulty - Hard

It was also in the afternoon. The interviewer was the member of the team I'll be working on if I get selected. He asked me some basic questions about related technologies.
Gave me 2-3 DS & Algo problems and asked me to solve them.

Q1. 
Array Sum Calculation
Calculate the sum of all elements in an array of length N.
Input:
Line 1: An integer N indicating the size of the array.
Line 2: N integers, the elements of the array, separated by ...read more
Ans. 
Calculate the sum of all elements in an array of length N.
• Iterate through the array and add each element to a running sum.

• Return the final sum as the output.
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Q2. 
Ninja and Alien Language Order Problem
An alien dropped its dictionary while visiting Earth. The Ninja wants to determine the order of characters used in the alien language, based on the given list of wor...read more
Ans. 
Determine the order of characters in an alien language based on a list of words.
• Create a graph where each character is a node and there is a directed edge from character 'a' to character 'b' if 'a' comes before 'b' in any word.

• Perform a topological sort on the graph to get the order of characters.

• Return the order as a string in lexicographical order.
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