Deutsche Telekom Digital Labs Senior Data Engineer Interview Questions and Answers

Q1. Implement Linked list
Ans. 
Linked list is a data structure where each node points to the next node.
• Create a Node class with data and next pointer

• Create a LinkedList class with head pointer

• Implement methods to add, remove, search, and traverse the list
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Q2. Implement Hash Map with array and linked list.
Ans. 
Implement Hash Map with array and linked list.
• Create an array of linked lists

• Hash function maps keys to array indices

• Insert key-value pairs into linked lists

• Handle collisions by chaining

• Search for a key by hashing and traversing linked list
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Q3. How to create a immutable class in java
Ans. 
To create an immutable class in Java, follow these steps:
• Make the class final

• Make all fields private and final

• Do not provide any setter methods

• Initialize all fields via constructor

• If any field is mutable, return a clone of it instead of the original object
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It has aptitude and coding based questions.For coding you can choose any coding language

There will be a GD for 7-10 people on random topic

Q1. 1st TR,ask to write a code of your preference.Linux commands,SQL
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Q1. 2nd TR ,ask about the projects you have done
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Q1. Basic HR round,where they will discuss about the company , job role etc
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Q1. Telecome domain related questions along with Unix shell scripting and SQL database question .
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Round duration - 120 minutes
Round difficulty - Easy

After round 1 there was a break of 15 mins and the coding round started.
We had a choice to attempt the exam in R language & SQL or python & sql
I chose python and sql
It had 8 questions 4 python and 4 sql

Q1. 
Longest Common Subsequence Problem Statement
Given two strings, S and T with respective lengths M and N, your task is to determine the length of their longest common subsequence.
A subsequence is a seque...read more
Ans. 
The task is to find the length of the longest common subsequence between two given strings.
• Use dynamic programming to solve this problem efficiently.

• Create a 2D array to store the lengths of longest common subsequences of substrings.

• Iterate through the strings to fill the array and find the length of the longest common subsequence.

• Example: For strings 'abcde' and 'ace', the longest common subsequence is 'ace' with leng
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Round duration - 15 minutes
Round difficulty - Medium

The interview was mostly analytical based and how you approach the round a few technical questions in dbms and oops were also asked.

Round duration - 20 Minutes
Round difficulty - Medium

Similar to first round
For Shortlists after elimination from first round.

Q1. 
Car Pooling Capacity Problem
You are a cab driver with a car that initially has 'C' empty seats. The car moves in a straight line towards the forward direction only. Your job is to determine if it is poss...read more
Ans. 
Determine if it is possible to accommodate all passenger trips within a car's capacity without exceeding it at any point.
• Iterate through each trip and keep track of the total number of passengers in the car at each point.

• Check if the total number of passengers exceeds the car capacity at any point.

• Return 'True' if all trips can be accommodated within the car capacity, otherwise return 'False'.
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Round duration - 20 minutes
Round difficulty - Easy

After two technical round interviews, the last round was a hr interview. The whole process can take up one whole day or more and your interview can be at any time
My process started at 5 pm and ended at 10:30 pm
All the interviewers were very friendly no pressure.

Q1. 
Nth Fibonacci Number Problem Statement
Calculate the Nth term in the Fibonacci sequence, where the sequence is defined as follows: F(n) = F(n-1) + F(n-2), with initial conditions F(1) = F(2) = 1.
Input:
...read more
Ans. 
Calculate the Nth Fibonacci number efficiently using dynamic programming.
• Use dynamic programming to store previously calculated Fibonacci numbers to avoid redundant calculations.

• Start with base cases F(1) and F(2) as 1, then iterate to calculate subsequent Fibonacci numbers.

• Time complexity can be optimized to O(N) using dynamic programming.

• Example: For N = 5, the 5th Fibonacci number is 5.
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Coding testing with 15 questions MCQ based

Q1. 1 or 2 DSA questions, rest tech stack related questions were asked
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Q1. This was a technofunctional round, kind of a managerial round.
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Q1. This was a HR round
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Q1. Reg BW and ABAP and XSA
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Q1. Reg sap BW and ABAP and XSA
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Q1. Company structure
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