Nielsen Devops Engineer Interview Questions and Answers

Round duration - 60 minutes
Round difficulty - Medium

This was a test round where 10 aptitude based questions were to be solved in 60 minutes

Q1. You have 5 pirates and 100 gold coins. The challenge is to determine how the pirates will divide the coins among themselves based on their ranking and the rules they follow.
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Round duration - 60 minutes
Round difficulty - Medium

They took us to the lab for this on and we were each given a paper with a program on it. It was all mixed as in each person got a different paper, You have around an hour to finish coding. after which you have to explain your code. They also gave wrong or incorrect inputs and see how your code handles these exceptions.

Q1. 
Reverse the String Problem Statement
You are given a string STR which contains alphabets, numbers, and special characters. Your task is to reverse the string.
Example:
Input:
STR = "abcde"
Output:
"e...read more
Ans. 
Reverse a given string containing alphabets, numbers, and special characters.
• Iterate through the string from the end to the beginning and append each character to a new string.

• Use built-in functions like reverse() or StringBuilder in languages like Python or Java for efficient reversal.

• Handle special characters and numbers along with alphabets while reversing the string.

• Ensure to consider the constraints provided in th...read more
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Q2. 
K Largest Elements Problem Statement
Given an unsorted array containing 'N' integers, you are required to find 'K' largest elements from the array and return them in non-decreasing order.
Input:
The fir...read more
Ans. 
Implement a function to find K largest elements in an unsorted array in non-decreasing order.
• Create a min heap of size K and insert the first K elements of the array

• For each remaining element, if it is larger than the root of the heap, replace the root with the element and heapify

• Finally, the heap will contain the K largest elements in non-decreasing order
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Q3. 
Remove Character from String Problem Statement
Given a string str and a character 'X', develop a function to eliminate all instances of 'X' from str and return the resulting string.
Input:
The first lin...read more
Ans. 
Develop a function to remove all instances of a given character from a string.
• Iterate through the string and build a new string excluding the specified character.

• Use a StringBuilder or similar data structure for efficient string manipulation.

• Handle edge cases like empty string or character not found in the input string.

• Ensure the function completes within the given time constraint.
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Q4. 
Triangle of Numbers Pattern
Ninja is tasked with printing a triangle pattern based on a given number 'N' for any test case.
Example:
Input:
N = 4
Output:
   1
  232
 34545
4567654
Explanation:
The pat...read more
Ans. 
Print a triangle pattern of numbers based on a given number 'N'.
• Iterate through each row and column to determine the numbers to print

• Use a combination of spaces and numbers to align the pattern correctly

• Increment the numbers in each row based on the row number
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Round duration - 60 minutes
Round difficulty - Easy

Compared to the other round this is more tech oriented. Lot more tech questions. It is of normal difficulty and is not that hard to clear, you only need to know the basics.
Very basic of Data Structure and Oracle knowledge enough. Lots of simple questions from data structures(insert into heaps etc). They did not ask to write code for DS, but rather to explain the logic through diagrams. For some complicated question, they expect how much you brainstorm ideas in solving

Q1. 
Convert Binary Tree to Mirror Tree
Convert a given binary tree into its mirror tree, where the left and right children of all non-leaf nodes are interchanged.
Input:
An integer ‘T’ denoting the number o...read more
Ans. 
Convert a binary tree into its mirror tree by interchanging left and right children of non-leaf nodes.
• Traverse the tree in postorder fashion and swap the left and right children of each node.

• Use recursion to solve the problem efficiently.

• Modify the binary tree in place without creating a new tree.
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Q2. 
Heap Sort Problem Statement
Given an array ARR consisting of N integers, your task is to use the Heap sort algorithm to arrange the array in non-decreasing order.
Input:
The first line of the input cont...read more
Ans. 
Implement the Heap sort algorithm to arrange an array in non-decreasing order.
• Implement the Heap sort algorithm to sort the given array in non-decreasing order

• Use a max heap to sort the array in non-decreasing order

• Time complexity of Heap sort is O(n log n)
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Q3. What is indexing in the context of databases?
Ans. 
Indexing in databases is a technique used to improve the speed of data retrieval by creating a data structure that allows for quick lookups.
• Indexes are created on specific columns in a database table to speed up queries that search for data in those columns.

• Indexes work similar to the index of a book, allowing the database to quickly locate the desired data without having to scan the entire table.

• Examples of indexes in...read more
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Q4. Which data structure is better for your use case: a B Tree or a Hash Table?
Ans. 
Hash Table is better for fast lookups and insertions, while B Tree is better for range queries and ordered traversal.
• Use Hash Table for fast lookups and insertions with O(1) average time complexity.

• Use B Tree for range queries and ordered traversal with O(log n) time complexity.

• Consider the size of the dataset and the specific operations needed to determine the best data structure.
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Round duration - 30 minutes
Round difficulty - Easy

This round lasted for around 30 minutes. It more of a character analysis round with a lot of HR type questions.

Round duration - 60 minutes
Round difficulty - Easy

10 Aptitude questions with difficulty level hard were asked in this test.

Q1. What is the minimum number of planes required to go around the world?
Ans. 
The minimum number of planes required to go around the world is one.
• One plane can fly around the world without needing to stop.

• The plane can refuel mid-air or carry enough fuel for the entire journey.

• Examples: Non-stop flights like the Boeing 787 Dreamliner or Airbus A350 can circumnavigate the globe with one plane.
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Round duration - 60 minutes
Round difficulty - Easy

Technical Interview round with questions based on data structures and algorithms. Questions about previous projects done and my roles on it and my leadership capabilities. Few technical questions from Threads and multi-processing.

Q1. 
Search in a Row-wise and Column-wise Sorted Matrix Problem Statement
You are given an N * N matrix of integers where each row and each column is sorted in increasing order. Your task is to find the positi...read more
Ans. 
Given a sorted N * N matrix, find the position of a target integer 'X'.
• Start from the top-right corner of the matrix and compare the target with the element at that position.

• Based on the comparison, move left or down in the matrix to narrow down the search.

• Repeat the process until the target is found or the search goes out of bounds.

• Return the position of the target if found, else return {-1, -1}.
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Q2. 
Rectangular Numbers Problem Statement
Ninja has a number 'N'. Your task is to generate a pattern where the outer rectangle is filled with the number 'N', and as you move inward, the numbers decrease conse...read more
Ans. 
Generate a pattern with outer rectangle filled with number 'N' and decreasing consecutively inward.
• Start by filling the outermost rectangle with the number 'N'.

• Decrease the numbers consecutively as you move inward towards the center.

• Continue this pattern until you reach the center of the rectangle.
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Round duration - 60 minutes
Round difficulty - Medium

DSA based questions were asked in this round. Questions on implementation of Linux directory structure were also asked.

Q1. 
Binary Array Sorting Problem Statement
You are provided with a binary array, i.e., an array containing only 0s and 1s. Your task is to sort this binary array and return it after sorting.
Input:
 The fir...read more
Ans. 
Yes, the binary array sorting problem can be solved in linear time and constant space using a single traversal.
• Use two pointers approach to swap 0s to the left and 1s to the right.

• Maintain two pointers, one for 0s and one for 1s, and swap elements accordingly.

• Example: Input: [1, 0, 1, 0, 1], Output: [0, 0, 1, 1, 1]
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Q2. 
Next Greater Element Problem Statement
You are given an array arr of length N. For each element in the array, find the next greater element (NGE) that appears to the right. If there is no such greater ele...read more
Ans. 
The task is to find the next greater element for each element in an array to its right, if no greater element exists, return -1.
• Iterate through the array from right to left and use a stack to keep track of elements.

• Pop elements from the stack until a greater element is found or the stack is empty.

• Store the next greater element for each element in the output array.
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Q3. What is the difference between Binary Search Trees (BST) and Tries?
Ans. 
BST is a binary tree structure where each node has at most two children, while Tries are tree structures used for storing strings.
• BST is used for searching, inserting, and deleting elements in a sorted manner.

• Tries are used for storing and searching strings efficiently.

• BST has a hierarchical structure with left and right child nodes.

• Tries have nodes representing characters, forming a tree-like structure for strings.

• Exa...read more
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Round duration - 60 minutes
Round difficulty - Easy

This was a technical round. Questions about previous projects and current one were asked. I was also asked about aptitude problems from the first round and how I understood and approached towards solution?

Q1. 
N Queens Problem
Given an integer N, find all possible placements of N queens on an N x N chessboard such that no two queens threaten each other.
Explanation:
A queen can attack another queen if they ar...read more
Ans. 
The N Queens Problem involves finding all possible placements of N queens on an N x N chessboard without threatening each other.
• Use backtracking algorithm to explore all possible configurations.

• Keep track of rows, columns, and diagonals to ensure queens do not threaten each other.

• Generate valid configurations recursively and backtrack when a solution is not possible.
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Q2. 
Form a Triangle Problem Statement
You are provided with an integer array/list ARR of length N. Your task is to determine if it is possible to construct at least one non-degenerate triangle using the value...read more
Ans. 
Check if it is possible to form a non-degenerate triangle using the sides provided in the array.
• Check if the sum of any two sides is greater than the third side for all combinations.

• If any such combination exists, return true; otherwise, return false.

• Handle multiple test cases as per the constraints provided.
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Round duration - 30 minutes
Round difficulty - Easy

Behavioral questions and team skills were discussed in this round.