Worldline Full Stack Engineer Interview Questions and Answers

Round duration - 75 minutes
Round difficulty - Easy

It was an online round taken through hackerrank. There were two coding questions of Easy level, Technical and Aptitude MCQs, that we had to solve.

Q1. 
Merge Intervals Problem Statement
You are provided with 'N' intervals, each containing two integers denoting the start time and end time of the interval.
Your task is to merge all overlapping intervals a...read more
Ans. 
Merge overlapping intervals and return sorted list by start time.
• Sort the intervals based on start time.

• Iterate through intervals and merge overlapping ones.

• Return the merged intervals sorted by start time.
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Q2. 
Count Distinct Substrings
You are provided with a string S. Your task is to determine and return the number of distinct substrings, including the empty substring, of this given string. Implement the solut...read more
Ans. 
Implement a function to count the number of distinct substrings in a given string using a trie data structure.
• Create a trie data structure to store the substrings of the input string.

• Traverse the trie to count the number of distinct substrings.

• Handle empty string as a distinct substring.

• Return the count of distinct substrings for each test case.
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Round duration - 15 Minutes
Round difficulty - Easy

It was a mix of Technical and Behavioural round.

Round duration - 30 minutes
Round difficulty - Easy

Final HR round for checking Compatibility with the Company.

Develop rate limiter logic which blocks an IP address when incoming request are > 50 within an arbitrary time frame that you determine.

Q1. Diff between react and jQuery
Ans. 
React is a modern JavaScript library for building user interfaces, while jQuery is a fast and concise JavaScript library for DOM manipulation.
• React is component-based, promoting reusability and modularity.

• React uses a virtual DOM for efficient updates, while jQuery directly manipulates the DOM.

• React is declarative, making it easier to reason about the UI, while jQuery is imperative.

• React is typically used for single-pa...read more
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Round duration - 90 minutes
Round difficulty - Medium

This was an online test for 90 minutes. 2 programming questions and MCQs related to CS fundamentals were asked.

Q1. 
Cycle Detection in a Singly Linked List
Determine if a given singly linked list of integers forms a cycle or not.
A cycle in a linked list occurs when a node's next points back to a previous node in the ...read more
Ans. 
Detect if a singly linked list forms a cycle by checking if a node's next points back to a previous node.
• Traverse the linked list using two pointers, one moving one step at a time and the other moving two steps at a time.

• If the two pointers meet at any point, it indicates the presence of a cycle in the linked list.

• If one of the pointers reaches the end of the list (null), it means there is no cycle.
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Q2. 
Palindrome Partitioning II Problem Statement
Given a string ‘str’, find the minimum number of partitions needed such that every segment of the string is a palindrome.
The task is to make cuts in the stri...read more
Ans. 
Find the minimum number of partitions needed in a string such that every segment is a palindrome.
• Iterate through the string and check for palindromes at each possible partition point.

• Use dynamic programming to keep track of the minimum cuts needed.

• Consider edge cases where the string is already a palindrome or consists of different characters only.
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Round duration - 60 minutes
Round difficulty - Medium

Technical round that lasted for around 60 minutes. The interviewer asked questions related to data structures and algorithms.

Q1. 
DFS Traversal Problem Statement
Given an undirected and disconnected graph G(V, E), where V is the number of vertices and E is the number of edges, the connections between vertices are provided in the 'GR...read more
Ans. 
DFS traversal problem on an undirected and disconnected graph to find connected components.
• Perform Depth First Search (DFS) on each vertex to find connected components

• Use a visited array to keep track of visited vertices

• Print the number of connected components and list vertices in ascending order for each component
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Q2. 
Cycle Detection in Undirected Graph Problem Statement
You are provided with an undirected graph containing 'N' vertices and 'M' edges. The vertices are numbered from 1 to 'N'. Your objective is to determi...read more
Ans. 
Detect cycles in an undirected graph with given vertices and edges.
• Use Depth First Search (DFS) to traverse the graph and detect cycles.

• Maintain a visited array to keep track of visited vertices and a parent array to keep track of the parent of each vertex.

• If while traversing, you encounter a visited vertex that is not the parent of the current vertex, then a cycle exists.

• Consider edge cases like disconnected graphs an
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Round duration - 60 minutes
Round difficulty - Medium

Technical round that lasted for around 60 minutes. The interviewer asked questions related to data structures and algorithms.

Q1. 
Merge Sort Problem Statement
You are given a sequence of numbers, ARR. Your task is to return a sorted sequence of ARR in non-descending order using the Merge Sort algorithm.
Explanation:
The Merge Sort...read more
Ans. 
Implement Merge Sort algorithm to sort a sequence of numbers in non-descending order.
• Implement the Merge Sort algorithm using a Divide and Conquer approach

• Recursively divide the input array into two halves until the size of each array is 1

• Merge the sorted halves to produce a completely sorted array

• Ensure the output is in non-descending order
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Q2. 
Maximum Difference Problem Statement
Given an array ARR of N elements, your task is to find the maximum difference between any two elements in ARR.
If the maximum difference is even, print EVEN; if it is...read more
Ans. 
Find the maximum difference between any two elements in an array and determine if it is even or odd.
• Iterate through the array to find the maximum and minimum elements

• Calculate the difference between the maximum and minimum elements

• Check if the difference is even or odd and return the result
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Q3. What is hashing and how can it be implemented?
Ans. 
Hashing is a process of converting input data into a fixed-size string of bytes using a hash function.
• Hashing is used to securely store passwords by converting them into a hash value before storing in a database.

• Hashing is used in data structures like hash tables to quickly retrieve data based on a key.

• Common hash functions include MD5, SHA-1, and SHA-256.

• Hashing can be implemented in programming languages like Python
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