Worldline Java Developer Interview Questions and Answers

Round duration - 90 minutes
Round difficulty - Medium

Started with projects discussion and internships and moved forward with coding problems.
It started at around 6:00 PM and lasted for 90 minutes approximately
The interviewer was very cool, he even gave me some tips on improving myself further at the end of the interview.

Q1. 
Longest Substring with At Most K Distinct Characters
Given a string S of length N and an integer K, find the length of the longest substring that contains at most K distinct characters.
Input:
The first...read more
Ans. 
Find the length of the longest substring with at most K distinct characters in a given string.
• Use a sliding window approach to keep track of the characters and their counts within the window.

• Maintain a hashmap to store the characters and their frequencies.

• Update the window size and characters count as you iterate through the string.

• Return the maximum window size encountered for each test case.
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Q2. 
Maximum Frequency Number Problem Statement
Given an array of integers with numbers in random order, write a program to find and return the number which appears the most frequently in the array.
If multip...read more
Ans. 
Find the number with the maximum frequency in an array of integers.
• Iterate through the array and keep track of the frequency of each number using a hashmap.

• Find the number with the maximum frequency and return it.

• If multiple elements have the same maximum frequency, return the one that appears first.
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Q3. 
Ninja and Bombs Problem Statement
Ninja wants to travel from his house to his best friend's house. The locations of the houses are on a 2D coordinate plane, where Ninja's house is located at the origin (0...read more
Ans. 
Determine if Ninja can reach his friend's house with even x-coordinate without using modulus operator.
• Check if the x-coordinate is even or odd by using bitwise AND operation with 1.

• Return 1 if x-coordinate is even, else return 0.

• Handle multiple test cases by iterating through each input.
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Round duration - 60 minutes
Round difficulty - Easy

I was asked a coding question then, a system design question and some basic operating systems and oops questions

Q1. 
Find Duplicates in an Array
Given an array ARR of size 'N', where each integer is in the range from 0 to N - 1, identify all elements that appear more than once.
Return the duplicate elements in any orde...read more
Ans. 
Find duplicates in an array of integers within a specified range.
• Iterate through the array and keep track of the count of each element using a hashmap.

• Return elements with count greater than 1 as duplicates.

• Time complexity can be optimized to O(N) using a set to store seen elements.
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Q2. Can you design a Google Search Engine?
Ans. 
Designing a Google Search Engine involves creating a web crawler, indexing system, and ranking algorithm.
• Develop a web crawler to discover and retrieve web pages.

• Implement an indexing system to store and organize the content of web pages.

• Design a ranking algorithm to determine the relevance of search results.

• Include features like autocomplete, spell check, and personalized search results.

• Optimize for speed and scalabil...read more
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Round duration - 90 minutes
Round difficulty - Medium

Only Java allowed

Q1. 
Sort 0 and 1 Problem Statement
Given an integer array ARR of size N containing only integers 0 and 1, implement a function to sort this array. The solution should scan the array only once without using an...read more
Ans. 
Sort an array of 0s and 1s in linear time without using additional arrays.
• Iterate through the array and maintain two pointers, one for 0s and one for 1s.

• Swap elements at the two pointers based on the current element being 0 or 1.

• Continue this process until the entire array is sorted in place.
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Round duration - 60 minutes
Round difficulty - Easy

Basic intro and coding questions

Q1. 
Valid Perfect Square Check
An integer N is provided, and the task is to determine if N is a perfect square. A perfect square refers to an integer which can be expressed as the square of another integer.
...read more
Ans. 
Implement a function to check if a given integer is a perfect square.
• Create a function that takes an integer as input and returns true if it is a perfect square, false otherwise.

• Iterate through possible square roots of the input integer and check if the square of the root equals the input.

• Return true if a perfect square is found, false otherwise.
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Q2. 
Merge Sort Problem Statement
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.
Example:
Input:
ARR = [5, 3, 8,...read more
Ans. 
Implement Merge Sort algorithm to sort a given sequence of numbers in non-descending order.
• Merge Sort is a divide-and-conquer algorithm that splits the array into two halves, recursively sorts each half, and then merges the sorted halves back together.

• Time complexity of Merge Sort is O(n log n) in the worst case scenario.

• It is a stable sorting algorithm, meaning that the relative order of equal elements is preserved.

• Ex...read more
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Round duration - 60 minutes
Round difficulty - Medium

More difficult than the previous round

Q1. 
Bottom View of Binary Tree Problem Statement
Given a binary tree, the task is to print its bottom view from left to right. Assume the left and the right child nodes make a 45-degree angle with their paren...read more
Ans. 
The task is to print the bottom view of a binary tree from left to right.
• Traverse the binary tree in level order and keep track of the horizontal distance of each node from the root.

• Store the nodes at each horizontal distance in a map, updating it as you traverse the tree.

• After traversal, extract the bottom-most nodes at each horizontal distance to get the bottom view sequence.
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Round duration - 70 minutes
Round difficulty - Medium

There were no DSA questions. My interviews were based on android app development. The interviewer presented scenarios and asked how will you solve them. No particular correct answer was expected just the best approach as per me.

Q1. How would you implement multiple RecyclerViews on a magnified screen in an Android application?
Ans. 
Implement multiple RecyclerViews on a magnified screen in an Android app by adjusting item sizes and spacing.
• Adjust item sizes and spacing based on screen magnification level

• Use nested RecyclerViews or custom layouts to display multiple lists

• Implement custom item decorators to manage spacing between RecyclerViews

• Consider using a GridLayoutManager with custom span sizes for each RecyclerView
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Q2. How would you implement various activities related to cart functionality in an e-commerce application?
Ans. 
Implementing cart functionality in an e-commerce application involves managing user interactions, updating quantities, handling discounts, and processing orders.
• Create a data structure to store cart items, quantities, and prices.

• Implement add to cart, remove from cart, and update quantity functionalities.

• Handle discounts, promotions, and coupon codes.

• Calculate total price, including taxes and shipping costs.

• Implement c...read more
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Round duration - 30 minutes
Round difficulty - Easy

HR asked questions about why Mobikwik, what's your goal, how are you a good fit, etc.

Round duration - 120 Minutes
Round difficulty - Medium

The first round was an assessment round comprised of MCQ questions of DSA, RDBMS, MySQL questions and 2 coding questions to be written in java only

Q1. 
Shortest Path in a Binary Matrix Problem Statement
Given a binary matrix of size N * M where each element is either 0 or 1, find the shortest path from a source cell to a destination cell, consisting only...read more
Ans. 
Find the shortest path in a binary matrix from a source cell to a destination cell consisting only of 1s.
• Use Breadth First Search (BFS) to explore all possible paths from the source cell to the destination cell.

• Keep track of visited cells to avoid revisiting them.

• Update the path length as you traverse through the matrix.

• Return the shortest path length found or -1 if no valid path exists.
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Q2. 
Kth Smallest Element Problem Statement
You are provided with an array of integers ARR of size N and an integer K. Your task is to find and return the K-th smallest value present in the array. All elements...read more
Ans. 
Find the K-th smallest element in an array of distinct integers.
• Sort the array and return the element at index K-1.

• Use a min-heap to find the K-th smallest element efficiently.

• Implement quickselect algorithm for optimal performance.
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Round duration - 60 Minutes
Round difficulty - Medium

The basic data structure round duration 1 hour, in this Interviewer, was very friendly and asked some casual questions. After that, he asked me to code.

Q1. 
Maximum Subarray Sum Problem Statement
Given an array of integers, determine the maximum possible sum of any contiguous subarray within the array.
Example:
Input:
array = [34, -50, 42, 14, -5, 86]
Out...read more
Ans. 
Find the maximum sum of any contiguous subarray within an array of integers.
• Iterate through the array and keep track of the maximum sum of subarrays encountered so far.

• At each index, decide whether to include the current element in the subarray or start a new subarray.

• Update the maximum sum if a new maximum is found.

• Example: For array [34, -50, 42, 14, -5, 86], the maximum sum is 137.

• Example: For array [-5, -1, -8, -9]
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Round duration - 60 Minutes
Round difficulty - Hard

Advance data structure round duration 1 hour, in this Interviewer asked some basic questions on oops, puzzles and asked me to code them later.

Q1. 
Reverse Linked List Problem Statement
Given a singly linked list of integers, return the head of the reversed linked list.
Example:
Initial linked list: 1 -> 2 -> 3 -> 4 -> NULL
Reversed link...read more
Ans. 
Reverse a singly linked list of integers and return the head of the reversed linked list.
• Iterate through the linked list and reverse the pointers to point to the previous node instead of the next node.

• Use three pointers to keep track of the current, previous, and next nodes while reversing the linked list.

• Update the head of the reversed linked list as the last node encountered during the reversal process.
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Q2. 
Trapping Rain Water
You are provided with an array ARR of integers representing an elevation map, where ARR[i] denotes the elevation of the ith bar. Determine the maximum amount of rainwater that can be t...read more
Ans. 
Given an array representing an elevation map, find the maximum amount of rainwater that can be trapped between the bars.
• Iterate through the array and calculate the maximum height on the left and right of each bar.

• Calculate the trapped water by finding the minimum of the maximum heights on the left and right minus the current bar height.

• Sum up the trapped water for all bars to get the total trapped rainwater.

• Example: Fo...read more
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Round duration - 30 Minutes
Round difficulty - Medium

Vice President interview round duration 30mins, in this round VP’s of different domains taking interview to the selected candidates.

Q1. 
Buy and Sell Stock Problem Statement
Imagine you are Harshad Mehta's friend, and you have been given the stock prices of a particular company for the next 'N' days. You can perform up to two buy-and-sell ...read more
Ans. 
The task is to determine the maximum profit that can be achieved by performing up to two buy-and-sell transactions on a given set of stock prices.
• Iterate through the array of stock prices to find the maximum profit that can be achieved by buying and selling stocks.

• Keep track of the maximum profit that can be obtained by performing two transactions.

• Consider all possible combinations of buying and selling stocks to maxim...read more
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Round duration - 30 Minutes
Round difficulty - Easy

This round lasted for 30mins basic HR questions were asked

Q1. Project discussion
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Round duration - 60 minutes
Round difficulty - Easy

I couldn't find an optimal approach to the first question, so she skipped that question and proceeded to next questions. Remaining questions I have answered satisfactorily.

Q1. 
Subset Sum Equal To K Problem Statement
Given an array/list of positive integers and an integer K, determine if there exists a subset whose sum equals K.
Provide true if such a subset exists, otherwise r...read more
Ans. 
Given an array of positive integers and an integer K, determine if there exists a subset whose sum equals K.
• Use dynamic programming to solve this problem efficiently

• Create a 2D array to store if a subset with a particular sum exists

• Iterate through the array and update the 2D array accordingly

• Check if the value at the end of the iteration is true for the given K
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Q2. 
BFS Traversal in a Graph
Given an undirected and disconnected graph G(V, E) where V vertices are numbered from 0 to V-1, and E represents edges, your task is to output the BFS traversal starting from the ...read more
Ans. 
BFS traversal in a disconnected graph starting from vertex 0.
• Implement BFS algorithm to traverse the graph starting from vertex 0.

• Use a queue to keep track of visited nodes and their neighbors.

• Ensure to print the traversal sequence in the correct order.

• Handle disconnected components by checking for unvisited nodes.

• Follow the BFS approach of exploring neighbors before moving to the next level.
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Round duration - 60 minutes
Round difficulty - Easy

I told that my strength is problem solving and I can always find a way when there is a bottle-neck. Gave some examples of my experiences while doing my assignments.

Q1. 
Replace Spaces in a String
Given a string STR consisting of words separated by spaces, your task is to replace all spaces between words with the characters "@40".
Input:
The first line contains an integ...read more
Ans. 
Replace spaces in a string with '@40'.
• Iterate through each character in the string

• Replace spaces with '@40'

• Return the modified string
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Round duration - 60 minutes
Round difficulty - Easy

Technical Interview Round with questions based on Data structures, OOPS and SQL.

Q1. 
Delete a Node from a Linked List
You are provided with a linked list of integers. Your task is to implement a function that deletes a node located at a specified position 'POS'.
Input:
The first line co...read more
Ans. 
Implement a function to delete a node from a linked list at a specified position.
• Traverse the linked list to find the node at the specified position.

• Update the pointers of the previous and next nodes to skip the node to be deleted.

• Handle edge cases such as deleting the head or tail of the linked list.

• Ensure to free the memory of the deleted node to avoid memory leaks.
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Q2. Write an SQL query to find the nth highest salary.
Ans. 
SQL query to find the nth highest salary
• Use the ORDER BY clause to sort salaries in descending order

• Use the LIMIT and OFFSET clauses to skip the first n-1 highest salaries

• Combine the above steps in a single query to find the nth highest salary
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Q3. Can you explain the concepts of Object-Oriented Programming (OOP)?
Ans. 
OOP is a programming paradigm based on the concept of objects, which can contain data in the form of fields and code in the form of procedures.
• OOP focuses on creating objects that interact with each other to solve problems.

• Key concepts include encapsulation, inheritance, and polymorphism.

• Encapsulation involves bundling data and methods that operate on the data into a single unit.

• Inheritance allows classes to inherit at...read more
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Round duration - 60 minutes
Round difficulty - Easy

Was asked me about my favorite technologies, What i liked about Facebook. And asked me to design a cinema ticket reservation web site­ like the one satyam has.

Q1. 
Kth Largest Element Problem
Given an array containing N distinct positive integers and a number K, determine the Kth largest element in the array.
Example:
Input:
N = 6, K = 3, array = [2, 1, 5, 6, 3, ...read more
Ans. 
Find the Kth largest element in an array of distinct positive integers.
• Sort the array in non-increasing order and return the Kth element.

• Handle multiple test cases efficiently.

• Ensure all elements in the array are distinct.
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Q2. What are virtual functions?
Ans. 
Virtual functions are functions in a base class that are overridden in derived classes to achieve runtime polymorphism.
• Virtual functions are declared in a base class with the 'virtual' keyword.

• They are overridden in derived classes using the 'override' keyword.

• They allow a function to be called based on the runtime type of an object.

• Virtual functions enable dynamic binding and late binding in C++.

• Example: virtual void ...read more
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Q3. Design a Cinema Ticket Reservation System.
Ans. 
Design a Cinema Ticket Reservation System
• Use a database to store movie information, showtimes, and seat availability

• Allow users to search for movies, select showtimes, and choose seats

• Implement a payment system for ticket purchases

• Send confirmation emails with QR codes for ticket validation
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Q4. In how many attempts can you find a defective ball among 10 given balls using a two-pan balance scale?
Ans. 
You can find a defective ball among 10 given balls in 2 attempts using a two-pan balance scale.
• Divide the 10 balls into two groups of 5 each.

• Weigh the two groups on the balance scale.

• If one group is heavier, it contains the defective ball. If they are equal, the defective ball is in the remaining 5 balls.

• Divide the group of 5 balls with the defective one into two groups of 2 and 3 balls.

• Weigh the two groups on the bala...read more
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Round duration - 30 minutes
Round difficulty - Easy

HR round that lasted for about 30 minutes. The interviewer asked me questions to know more about me and a puzzle.

Q1. Can you tell me about your projects and your extracurricular activities?
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Round duration - 90 minutes
Round difficulty - Medium

It was conducted in Hacker rank which consisted of 10 aptitude questions that included C, C++, Java MCQ. 2 programming questions were also given.

Q1. 
Minimum Cost Path Problem Statement
Given an N x M matrix filled with integers, determine the minimum sum obtainable from a path that starts at a specified cell (x, y) and ends at the top left corner of t...read more
Ans. 
The problem involves finding the minimum sum path from a specified cell to the top left corner of a matrix.
• Start from the specified cell and calculate the minimum sum path to reach the top left corner using dynamic programming.

• Consider the three possible moves: down, right, and down-right diagonal.

• Keep track of the minimum sum at each cell and update it based on the minimum of the three possible moves.

• Finally, the mini...read more
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Q2. 
Balanced Parentheses Combinations
Given an integer N representing the number of pairs of parentheses, find all the possible combinations of balanced parentheses using the given number of pairs.
Explanati...read more
Ans. 
Generate all possible combinations of balanced parentheses for a given number of pairs.
• Use backtracking to generate all possible combinations of balanced parentheses.

• Keep track of the number of open and close parentheses used in each combination.

• Recursively generate combinations by adding open parentheses if there are remaining, and closing parentheses if the number of open parentheses is greater than the number of clo...read more
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Round duration - 60 minutes
Round difficulty - Medium

Technical round with questions based on data structures, oops and networking.

Q1. 
Character Counting Challenge
Create a program that counts and prints the total number of specific character types from user input. Specifically, you need to count lowercase English alphabets, numeric digi...read more
Ans. 
Create a program to count lowercase alphabets, digits, and white spaces from user input until '$' is encountered.
• Read characters from input stream until '$' is encountered

• Count lowercase alphabets, digits, and white spaces separately

• Print the counts of each character type as three integers separated by spaces
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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. 
Find K largest elements in an unsorted array and return them in non-decreasing order.
• Sort the array in non-decreasing order.

• Return the last K elements of the sorted array.
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Q3. How can you check whether you have an internet connection on your system?
Ans. 
To check internet connection on a system, you can use various methods like pinging a website or checking network status.
• Use ping command to check connectivity to a website (e.g. ping www.google.com)

• Check network status using network settings or command line tools

• Try accessing a website or online service to verify internet connection
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Q4. What happens when you type a URL in a web browser?
Ans. 
When you type a URL in a web browser, the browser sends a request to the server hosting the website, which then responds with the necessary files to display the webpage.
• Browser checks cache for DNS resolution

• If not found, browser sends a DNS query to resolve the domain name to an IP address

• Browser establishes a TCP connection with the server

• Browser sends an HTTP request to the server for the webpage

• Server processes the...read more
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Round duration - 60 minutes
Round difficulty - Medium

Technical round with questions based on data structures, oops and networking.

Q1. 
Counting Sort Problem Statement
Ninja is learning about sorting algorithms, specifically those that do not rely on comparisons. Can you help Ninja implement the counting sort algorithm?
Example:
Input:
...read more
Ans. 
Implement counting sort algorithm to sort an array of integers without comparisons.
• Count the frequency of each element in the input array.

• Calculate the prefix sum of frequencies to determine the position of each element in the sorted array.

• Place each element in its correct position based on the prefix sum.

• Time complexity of counting sort is O(n+k), where n is the number of elements and k is the range of input.

• Example: ...read more
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Q2. What are the applications of the Fibonacci series in real life?
Ans. 
The Fibonacci series has applications in various fields such as mathematics, computer science, art, and nature.
• Used in algorithms for optimization problems and dynamic programming.

• Found in nature, such as the arrangement of leaves on a stem, the branching of trees, and the spiral shapes of shells.

• Applied in financial markets for predicting stock prices and analyzing market trends.

• Utilized in art and design for creating
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Round duration - 30 minutes
Round difficulty - Easy

HR round where the interviewer asked questions to know more about me.