Jd Sports Fashion Plc DOT NET Developer Interview Questions and Answers

2 DSA questions and some MCQ on Java and Spring

Q1. Longest palindromic substring
Ans. 
A palindromic substring is a string that reads the same forwards and backwards.
• Use dynamic programming to find the longest palindromic substring.

• Start by considering each character as the center of a potential palindrome.

• Expand outwards from each center to check for palindromes of odd and even lengths.
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Q2. Remove duplicates in place from a 1D array
Ans. 
Remove duplicates from a 1D array of strings in place
• Iterate through the array and use a HashSet to keep track of unique elements

• Replace duplicates with null or an empty string to remove them in place
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Q1. Project discussion
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Q2. Search min element in a rotated sorted array with duplicate elements
Ans. 
Search for the minimum element in a rotated sorted array with duplicate elements.
• Use binary search to find the minimum element in the rotated sorted array.

• Handle the case where duplicate elements are present by adjusting the search conditions.

• Consider cases where the array is not rotated or contains only one element.
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Q3. Ways of declaring singleton class
Ans. 
A singleton class is a class that can only have one instance created throughout the application.
• Declare a private static instance variable of the class

• Create a private constructor to prevent external instantiation

• Provide a public static method to access the instance
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Q1. Project discussion
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Q2. Behavioural questions
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2 coding questions from dsa. one quest was from trees ds

Q1. Why did you choose target
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Q2. Minus points in you that you can share with us
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Question about basic engineering subjects and coding

Q1. Interview about technical question
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Q2. Fabinocci series,trees
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Q1. C# basic questions and asp.net
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Q2. C# basic questions about properties, object, class
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Q1. Why string arr immutable
Ans. 
String arrays are immutable because they cannot be changed once created.
• Strings in an array cannot be modified individually

• Any changes to a string array result in a new array being created

• Immutable arrays ensure data integrity and prevent unintended side effects
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Q2. How we can create a custom immutable class
Ans. 
To create a custom immutable class, use final keyword for class, private final fields, and no setter methods.
• Use the final keyword for the class to prevent inheritance

• Declare all fields as private and final to prevent modification

• Do not provide setter methods for the fields to maintain immutability

• Provide getter methods to access the fields
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Round duration - 90 minutes
Round difficulty - Medium

This was a proctured online coding round where we had 2 questions to solve under 90 minutes . The questions were a bit lengthy but the implementation part was quite easy .

Q1. 
Encode the Message Problem Statement
Given a text message, your task is to return the Run-length Encoding of the given message.
Run-length encoding is a fast and simple method of encoding strings, repres...read more
Ans. 
Steps:
1) Sort all the words in descending order of their lengths.
2) Initialise res with first word in the vector + "#"
3) Now we just need to find, if other words in the vector + # are substring of res or not. if not, append that word to res.
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Q2. 
Make All Elements of the Array Distinct
Given an array/list ARR of integers with size 'N', your task is to determine the minimum number of increments needed to make all elements of the array distinct. You...read more
Ans. 
Steps:
1) The idea is to sort the input , then we move forward from the beginning of the array till the end.
2) As soon as we found a condition that the current element is less than or equal to the previous elements then we need to update the current array element by adding 1 to its prev element .
3) At the same time we need to keep track of result by result += A[i-1]- A[i]+1;
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Round duration - 50 Minutes
Round difficulty - Easy

This Round was DS/Algo + Core round and it started with formal introduction, followed by 3 problems. We first dicussed the
approach the time complexity and proper code covering all cases for the 2 coding problems . The last question was related to OS and was a bit theoretical .

Q1. 
Distinct Characters Problem Statement
Given a string STR, return all possible non-empty subsequences with distinct characters. The order of the strings returned is not important.
Example:
Input:
STR = ...read more
Ans. 
Instead of counting all unique characters and struggling with all possible substrings,
we can count for every char in S, how many ways to be found as a unique char.
We count and sum, and it will be out answer.

Let, index[26][2] record last two occurrence index for every upper characters.
1) Initialise all values in index to -1.
2) Loop on string S, for every character c, update its last two occurrence index to index[c].
3) C...read more
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Q2. 
Calculate Score of Balanced Parentheses
In this intellectual game, Ninja is provided with a string of balanced parentheses called STR. The aim is to calculate the score based on specific game rules. If Nin...read more
Ans. 
Approach 1 : 

Every position in the string has a depth - some number of matching parentheses surrounding it. For example, the dot in (()(.())) has depth 2, because of these parentheses: (__(.__))

1) Our goal is to maintain the score at the current depth we are on. 
2) When we see an opening bracket, we increase our depth, and our score at the new depth is 0. 
3) When we see a closing bracket, we add twice th...read more
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Q3. Can you explain demand paging?
Ans. 
Demand paging is a method that loads pages into memory on demand. This method is mostly used in virtual memory. In this, a page is only brought into memory when a location on that particular page is referenced during execution. The following steps are generally followed:

1) Attempt to access the page.
2) If the page is valid (in memory) then continue processing instructions as normal.
3) If a page is invalid then a page-f...read more
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Round duration - 40 Minutes
Round difficulty - Medium

I was given 2 preety good questions of DSA in this round . One was related to Binary Trees and the other was a good DP problem in which I struggled a bit but with some hints I was able to solve this problem too . The last question was related to OOPS and was preety easy .

Q1. 
Binary Tree Construction from Traversals Problem
Given the POSTORDER and PREORDER traversals of a binary tree, where the tree consists of N nodes with each node representing a distinct positive integer fr...read more
Ans. 
We will preorder to generate TreeNodes, push them to the stack and perform postorder to pop them out.

1) Iterate on pre array and construct node one by one.
2) Stack saves the current path of the tree.
3) node = new TreeNode(pre[i]), if not left child, add node to the left. otherwise add it to the right.
4) If we meet a same value in the pre and post, it means we have completed the construction for current subtree. We pop
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Q2. 
Minimum Cost to Buy Oranges Problem Statement
You are given a bag of capacity 'W' kg and a list 'cost' of costs for packets of oranges with different weights. Each element at the i-th position in the list...read more
Ans. 
This problem was actually a variation Unbounded Kanpsack Problem . I first gave the interviewer a naive recursive
approach and then later optimised it using memoisation .

Naive Recursive Approach :

1) Create a recursive function ( int minCost(cost, idx , w) ) which returns the optimal answer for an array which starts
with index idx and for a given weight w.

2) Now for every index idx , if cost[idx]!=-1 then I have three opt...read more
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Q3. Can you explain the concepts of static and dynamic polymorphism in Object-Oriented Programming?
Ans. 
Static polymorphism (static binding) is a kind of polymorphism that occurs at compile time. An example of compile-time polymorphism is method overloading.

Runtime polymorphism or dynamic polymorphism (dynamic binding) is a type of polymorphism which is resolved during runtime. An example of runtime polymorphism is method overriding.
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Round duration - 30 Minutes
Round difficulty - Easy

This is a cultural fitment testing round .HR was very frank and asked standard questions. Then we discussed about my role.

Q1. Why should we hire you?
Ans. 
Tip 1 : The cross questioning can go intense some time, think before you speak.
Tip 2 : Be open minded and answer whatever you are thinking, in these rounds I feel it is important to have opinion.
Tip 3 : Context of questions can be switched, pay attention to the details. It is okay to ask questions in these round,
like what are the projects currently the company is investing, which team you are mentoring. How all is the ...read more
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Q2. What do you know about the company?
Ans. 
General Tip : Before an interview for any company , have a breif insight about the company , what it does , when was
it founded and so on . All these info can be easily acquired from the Company Website itself .
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Basic java question, design questions, 1 data structure question

Q1. Asked puzzle and previous project experience
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Q2. Monitor microservices using Spring actuator
Ans. 
Spring Actuator provides endpoints to monitor and manage microservices in a Spring Boot application.
• Add Spring Boot Actuator dependency in pom.xml

• Enable Actuator endpoints in application.properties or application.yml

• Access Actuator endpoints like /actuator/health, /actuator/info, etc.

• Customize Actuator endpoints using configuration properties
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Q3. How webflux works
Ans. 
Webflux is a reactive programming framework for building non-blocking, event-driven applications on the JVM.
• Webflux is part of the Spring Framework and provides support for reactive programming.

• It allows developers to build asynchronous, non-blocking applications that can handle a large number of concurrent connections.

• Webflux uses Project Reactor, a reactive library for building reactive applications.

• It supports both ...read more
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Round duration - 120 minutes
Round difficulty - Medium

This was the online round held at Hackerearth. All students who met the eligibility criteria were shared link for the online test on hackerearth.

Q1. 
Remove Consecutive Duplicates Problem Statement
Given a string str of size N, your task is to recursively remove consecutive duplicates from this string.
Input:
T (number of test cases)
N (length of the ...read more
Ans. Recursion
The idea is here to use recursion as mentioned in the problem statement. For each character either it will be included in the answer or not, how to decide this at each point?
We will compare the last and 2nd last character of the string each time if they are equal we will remove the last and call recursion for the remaining string, if they both are not equal then we will append the last character into our final...read more
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Q2. 
Deepest Leaves Sum Problem Statement
Given a binary tree of integers, your task is to calculate the sum of all the leaf nodes present at the deepest level of this binary tree. If there are no such nodes, ...read more
Ans. Find Deepest Level
The idea is pretty simple. First, we will find the deepest level of the given binary tree, say ‘maxDepth’. We can do this with a single traversal of the binary tree. 

After finding the deepest level of the binary tree, we will again traverse the given tree. Also, we will maintain a ‘sum’ and ‘currLevel’ variable for each node in the tree. Whenever the ‘currLevel’ which represents the level of the ...read more
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Round duration - 60 minutes
Round difficulty - Medium

This Round was DS and Algo round and it started with formal introduction, followed by 2 problems.There were 2 interviewers. We first dicussed the approach the time complexity and proper code covering all cases.

Q1. 
Palindrome Permutation - Problem Statement
Determine if a permutation of a given string S can form a palindrome.
Example:
Input:
string S = "aab"
Output:
"True"
Explanation:
The permutation "aba" o...read more
Ans. Frequency Table
1. The idea behind this approach is that in a palindrome at max 1 character can have an odd frequency.
2. So in this approach, we calculate the frequency of each character of the given string and check if at most 1 character has an odd frequency. If more than one character will be having the odd frequency then the given string can not be converted into a palindrome.
3. Therefore, we create a frequency table, (say ‘...read more
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Q2. 
Word Presence in Sentence
Determine if a given word 'W' is present in the sentence 'S' as a complete word. The word should not merely be a substring of another word.
Input:
The first line contains an in...read more
Ans. Brute Force
The basic idea of this approach is to check each word of the given sentence ‘S’ if it matches with the given word ‘W’.

 
Consider the following steps:
1. Start iterating through each character of sentence string ‘S’ using a variable ‘i’ such that 0 <= ‘i’ < |S|
   • Create a string “temp” which stores the current word.
   • Add all the subsequent characters of the sentence till space is detected or if all end of th...read more
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Round duration - 30 mintues
Round difficulty - Easy

This is a cultural fitment testing round .HR was very frank and asked standard questions. Then we discussed about my role.