CodeNation Interview Questions, Process, and Tips

Round duration - 90 minutes
Round difficulty - Hard

The test was from 10 pm to 11:30 pm at night, Since we had to give the test from home so it was not an uncomfortable timing for me. The test was conducted on hackerrank. Personally I find Hackerrank a better test platform than others like Amcat or Mettle.

Q1. 
Minimum Fountains Activation Problem
In this problem, you have a one-dimensional garden of length 'N'. Each position from 0 to 'N' has a fountain that can provide water to the garden up to a certain range...read more
Ans. 
Find the minimum number of fountains to activate to water the entire garden.
• Iterate through the array to find the coverage of each fountain.

• Keep track of the farthest coverage reached by activating fountains.

• Activate the fountain that covers the farthest distance to minimize the number of fountains activated.
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Q2. 
Count Inversions Problem Statement
Given an integer array ARR of size N, your task is to find the total number of inversions that exist in the array.
An inversion is defined for a pair of integers in the...read more
Ans. 
Count the total number of inversions in an integer array.
• Iterate through the array and for each pair of elements, check if the inversion condition is met.

• Use a nested loop to compare each pair of elements efficiently.

• Keep a count of the inversions found and return the total count at the end.
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Q3. 
Array Transformation Problem
Given an array ARR consisting of N integers and a non-negative integer K. An operation on the array replaces each element ELE with MX - ELE, where MX is the maximum element of...read more
Ans. 
Given an array and a non-negative integer K, perform K operations on the array by replacing each element with MX - element, where MX is the maximum element of the array.
• Find the maximum element in the array.

• Perform the operation on each element K times.

• Update the array after each operation.

• Print the transformed array elements after K operations.
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Round duration - 90 minutes
Round difficulty - Hard

This interview was at 10 am in the morning and was taken by a SDE 3 of the company who had a very great background in Competitive Coding.
The interview started with me introducing myself. The interviewer then gave me a google doc which had 2 coding questions written . He asked me to go through the first question and explain the approach. After which he asked me to code the solution as well. Same procedure was followed for the second question. The most difficult part in using Google Doc to write code is that it doesn't has automatic indentation like the code editors, so I had to put much efforts in keeping my code readable.

Q1. 
Count Distinct Bitwise OR of All Subarrays
Given an array of positive integers, determine the number of distinct values obtained by applying the bitwise OR operation on all possible subarrays.
Explanatio...read more
Ans. 
Count distinct values obtained by applying bitwise OR operation on all possible subarrays of an array of positive integers.
• Use a set to store distinct values obtained by bitwise OR operation on all subarrays.

• Iterate through all subarrays efficiently to calculate distinct values.

• Optimize the solution to handle large input sizes efficiently.

• Handle bitwise OR operation on subarrays using bitwise operators.

• Consider using d...read more
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Q2. 
Graph Coloring Problem
You are given a graph with 'N' vertices numbered from '1' to 'N' and 'M' edges. Your task is to color this graph using two colors, such as blue and red, in a way that no two adjacen...read more
Ans. 
The task is to color a graph with two colors in a way that no two adjacent vertices share the same color.
• Check if the graph can be colored using two colors without any adjacent vertices sharing the same color.

• Use graph coloring algorithms like BFS or DFS to solve the problem.

• If there are odd cycles in the graph, it is not possible to color the graph as described.

• If the graph is bipartite, then it is possible to color t
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Round duration - 60 minutes
Round difficulty - Hard

The round was at 4 pm evening. This round was taken by one of the Vice President of the company, this made me anxious from the very beginning.
The interviewer was a knowledgeable man and had great knowledge in every field. He always demanded exact answers.
The round started with my resume walk through. Then came open ended questions followed by a system design question in which I failed miserably.

Round duration - 45 Minutes
Round difficulty - Medium

This was a straight coding round with three questions , I was able to solve all 3

Q1. 
Kth Largest Number Problem Statement
You are given a continuous stream of numbers, and the task is to determine the kth largest number at any moment during the stream.
Explanation:
A specialized data st...read more
Ans. 
Design a data structure to find the kth largest number in a continuous stream of integers.
• Design a specialized data structure to handle continuous stream of numbers

• Implement add(DATA) function to add integers to the pool

• Implement getKthLargest() function to retrieve the kth largest number

• Maintain the pool of numbers and update it based on queries

• Output the kth largest number for each Type 2 query
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Q2. 
Rat in a Maze Problem Statement
You need to determine all possible paths for a rat starting at position (0, 0) in a square maze to reach its destination at (N-1, N-1). The maze is represented as an N*N ma...read more
Ans. 
Find all possible paths for a rat in a maze from source to destination.
• Use backtracking to explore all possible paths in the maze.

• Keep track of visited cells to avoid revisiting them.

• Recursively try moving in all directions (up, down, left, right) until reaching the destination.

• Add the valid path to the result list when the destination is reached.

• Sort the result list in alphabetical order before returning.
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Round duration - 60 Minutes
Round difficulty - Medium

As this was my first system design round, I was not expecting to be able to tell anything , but to my surprize he interested in just the idea what I can think , how I can solve some issues which need not be definitely to have a solution / or multiple solutions are possible from common sense.

I was given an Idea based question