OneCode Interview Questions and Answers

You should be familiar with core java features. Collections, converting one collection Array / Vector to other. Removing duplicates. Lambda chaining / Functional programming. Basic SQL - Joins, Aggregates etc.

Q1. Explain Architecture of applications you worked on. Justify use of components. System Design questions.
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Q1. How does reconciliation happens in AEPS
Ans. 
Reconciliation in AEPS involves matching the transactions between the bank and the service provider to ensure accuracy.
• Reconciliation involves comparing the transactions recorded by the bank with those recorded by the service provider.

• Any discrepancies are identified and resolved to ensure accurate financial records.

• Reconciliation helps in detecting errors, fraud, or any other discrepancies in the transactions.

• Examples...read more
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Q2. Tell me about yourself
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1hr aptitude + coding

Q1. Next Greater Element in an array
Ans. 
Find the next greater element in an array for each element
• Iterate through the array and for each element, find the next greater element

• Use a stack to keep track of elements whose next greater element is not yet found

• If the current element is greater than the top element of the stack, pop the stack and mark the popped element's next greater element as the current element

• Push the current element onto the stack

• If there ar...read more
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Q2. Question based on Sql inner join
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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.