Write a code to delete the middle element of a stack without using any additional data structure while preserving the original order. Input: [1, 2, 3, 4, 5]. Output: [1, 2, 4, 5]
WellDev Ltd
| Founding year | |
| Company Website | https://www.welldev.io/ |
| Career Website | https://www.welldev.io/careers |
| Technologies Used | Ruby on Rails, Android, iOS, ReactJS |
Introduction
WellDev Ltd is a software company based in Zurich, Switzerland, specializing in software development and IT services. It has offices in Bangladesh (Dhaka), South Africa, Canada etc.
Interview Stages
- Initial Screening: After dropping CV they take a MCQ Round, almost every candidate gets an email for participation in this round.
- Round 1: The first round is a technical round and generally lasts for an hour.
- Round 2: The second round is divided into two part. The first part is a behavioural part taken by HR of the company. For the second part two software engineer conducts the technical sessions.
- COO Round: The final round is taken by the COO of the company
Preliminary Round
A Broad Range of Topics
This round consisted of a multiple-choice questionnaire covering these topics. The test required me to share my screen with Quillgo and keep my camera on. It covers wide range of topics like JavaScript fundamentals, OOP, DBMS, SWE principles, Networking, Rest API knowledge, Analytical reasoning, DSA (time complexity, sorting, binary trees, MST, greedy algorithms).
First Round Questions
Hands-On Problem Solving
What will the output of this code in C Programming Language and why?
C
int arr[3] = {1, 2, 3};
if(&arr[0] == &arr){
printf("They are the same!");
}else {
printf("Not same");
}Given an array, what will be the base address if we print the array name only (e.g., printf(ara))?
What is the time complexity of the print statement? if it's O(1) why is that? Is it the same case for Linked List? If it's not, why it isn't the same case?
python
arr = [1, 2, 3, 4]
print(arr[2])Can we run binary search on a sorted LinkedList? If we can, what issues we might face?
python
def fn(n):
if n == 0:
return 0
return n + fn(n-1)Given the above function, rename the function according to what the function tries to achive.
2nd Iteration: Write the same function but in a iterative manner. Does the both implementations have same Time Complexity and Space Complxity?
What is the time complexity of the following code?
C
int fun(int n) {
if(n <= 1) return n;
int x = fun(n - 1);
int y = fun(n - 2);
return x + y;
}Explain the order of SQL query execution (e.g., FROM, WHERE, GROUP BY, HAVING, SELECT).
Given a table with redundant data in multiple columns, how would you optimize it? (Hint: Normalization)
Given a Java code, identify issues that violate access modifiers.
Explain the basic concepts of Object-Oriented Programming (OOP).
What are the ACID properties in DBMS?
A basic GRE-like math question.
Write a SQL query to show all the duplicate rows in a table.
Can we make a stack with a queue?
Second Round Questions
Write an API call to check whether the system is running properly and explain a GET API call.
Write a code to create a directory and a text file inside it with “Hello World” written.
What happens if two people try to reserve the same ticket simultaneously in a ticket reservation system? How would you solve this problem in a ticket management system? What will be your idea in this regard?
How many APIs are required to solve the above ticket reservation problem?
How can passwords be secured so that no one (even the administrator) can view them? How can password hashing be strengthened? What techniques do you know? (Hint: Salting and hashing techniques)
What is a trigger in DBMS, and what does cascading mean?
If we need to display a large amount of data on a website, what technique should be followed? (Hint: Pagination)
What happens when we browse a website? How are the contents rendered?
What is the difference between SQL and NoSQL?
For storing values from cache memory to RAM, should we use SQL or NoSQL?
Given an array of integers heights representing the histogram's bar height where the width of each bar is 1, return the area of the largest rectangle in the histogram.
You have a n-story building, and two eggs. An egg will break if dropped from a certain height (ie above a floor f). Determine the minimum number of moves that you need to determine with certainty what the value of f is.
Given a table with product_id, price, and product_name, write a query to find products with the same price.
What is the difference between DELETE, TRUNCATE, and DROP in SQL?
Explain threading in OOP.
How do you check for changes in a database?
Many questions from my CV (all practical, not just asking what you have done).
Given an integer array nums, move all 0's to the end of it while maintaining the relative order of the non-zero elements.
Behavioral questions
Could you please introduce yourself? where do you live? Who is there in your family?
Where do you wanna see yourself after 5years?
If you could devote yourself to learn new technologies?
What is your strength and weakness?
Do you have a plan to join full-time after successfully passing the training program?
Why should we hire you?
What is your salary expectation?
How you will deal with a tough co-worker
If you have a tight deadline and will miss it that time, how will you handle it?
Tell me something that will convince me to hire you.
How do you balance between a tight deadline and preserving best practices for?
what stack u wanna work with, do you wanna go abroad?
How would your friends, parents, and teachers describe you?
3 word to describe yourself?
What are your expectations from WellDev as a workplace?
What is the motivation to apply here?
Coding Questions
Write pseudocode of generating fibonacci number using only two variable
Given the root of a binary tree, return the postorder traversal of its nodes' values.
Given an array of integers nums and an integer target, return all pairs of indices of the two numbers such that they add up to target.
Sort an array that consists with elements of odd numbers.
Given an array representing preorder traversal of BST, print its postorder traversal.
Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j and j != k and i != k and nums[i] + nums[j] + nums[k] == 0.
Given an array of strings, group the anagrams together. You can return the answer in any order.
Basic recursive implementation problem
Given two variables, write a code to swap them without using any additional variable.
Printing cumulative sum
Given a chessboard, there are some knights placed initially. How can we place some another knights in such a way so that no one attacked each other.
Find the second highest element in a given array.
SQL Questions
Write SQL query to find unique column of a database
Write SQL query to find second highest salary
Write SQL query to sort salary in descending order
Short Questions
Write the output of the following code:
cpp
int i = 5;
cout << i++ << endl;
cout << ++i << endl;How to iterate a binary search tree in reverse order?
Write a function to describe polymorphism
How to describe a graph on code
Details on Two pointers
What is abstract class?
Explain how insertion sort works
Describe Encapsulation with examples?
Which performs better Linked List or Array?
Deletion and insertion of circular linked list Data structures used in DFS and BFS?
What are the advantages and disadvantages of Linked List?
Describe Singleton pattern.
Describe database normalization
Which http codes are used for success and failure?
Finding network address
BFS, DFS, Mergesort, Quicksort, Recursion
Which data structure is good to use to search strings?
What's the difference between selection sort and insertion sort?
Explain ER Diagram in Relational Database.
What is a Circular linked ist?
what is the difference between graph and tree?
What is kernel in os?
Difference between left outer join and right outer join?
What do you understand by the term Dependency Injection?
What are protected and public variables?
What is the JavaScript event in a document?
What steps do you take to improve UI design?
Give me a short description of polymorphism?
What is the difference between array and linked list?
Describe Stack & Queue?
Difference between polymorphism and constructor overloading?
How to reverse a linked list?