Hippo Stores Front end Developer Interview Questions and Answers

Q1. Unique elements in an array using es6
Ans. 
Using Set and spread operator to get unique elements in an array.
• Create a Set from the array using Set constructor

• Use spread operator to convert Set back to array

• Alternatively, use Array.from() method to convert Set to array
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Coding question of react application.

Q1. Project related discussion.
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Speed distance time basic

Q1. DSA oops sql project basic
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Q2. Oops basic questions
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Q1. Group discussion basic
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Q2. Basic questions in project in resume
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Round duration - 90 minutes
Round difficulty - Medium

This was a proctured online coding round where we had 2 questions to solve under 90 minutes . The questions were of easy to medium level I would say with some lenghty implementations .

Q1. 
Minimum Numbers Required Problem Statement
Given an array 'ARR' consisting of N integers, along with two integers, 'SUM' and 'MAXVAL', you need to determine the minimum number of integers to be added to t...read more
Ans. 
Determine the minimum number of integers to be added to an array to make its sum equal to a given value.
• Iterate through the array and calculate the current sum.

• Determine the difference between the target sum and the current sum.

• Add the minimum number of integers within the range of -MAXVAL to MAXVAL to reach the target sum.
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Q2. 
Maximum Sum Subsequence Problem Statement
Given an array of integers NUMS consisting of N integers and an integer K, determine the maximum sum of an increasing subsequence with exactly K elements.
Exampl...read more
Ans. 
Find the maximum sum of an increasing subsequence with exactly K elements in an array of integers.
• Iterate through the array and maintain a dynamic programming table to store the maximum sum of increasing subsequences ending at each index.

• For each element, check all previous elements to find the increasing subsequence with maximum sum ending at that element.

• Update the dynamic programming table with the maximum sum found...read more
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Round duration - 50 Minutes
Round difficulty - Medium

Standard Data Structures and Algorithms round . One has to be fairly comfortable in solving algorithmic problems to
pass this round with ease.

Q1. 
Check Whether Binary Tree Is Complete
You have been given a binary tree and your task is to determine if it is a Complete Binary Tree or not.
A Complete Binary Tree is defined as a binary tree where ever...read more
Ans. 
Check if a binary tree is a Complete Binary Tree or not based on given criteria.
• Traverse the binary tree level by level and check if all levels are completely filled except the last one.

• Ensure all nodes at the last level are positioned at the leftmost side.

• Use level order traversal to check for completeness of the binary tree.

• Example: For input 1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -1, the output should be 1.
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Q2. 
Consecutive Elements
Given an array arr of N non-negative integers, determine whether the array consists of consecutive numbers. Return true if they do, and false otherwise.
Input:
The first line of inp...read more
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Round duration - 40 Minutes
Round difficulty - Medium

This round majorly focused on my projects and some standard questions revolving around Operating Systems and DBMS.

Q1. How can you print numbers from 1 to 100 using more than two threads in an optimized approach?
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Q2. What are the advantages of using views in a database management system?
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Round duration - 30 Minutes
Round difficulty - Easy

This is a cultural fitment testing round .HR was very frank and asked standard questions. Then we discussed about my role.

Q1. What do you know about the company?
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Q2. Why should we hire you?
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Round duration - 60 Minutes
Round difficulty - Medium

There were 2 coding questions given in this round. One was related to Dynamic Programming and the second one was related to Recursion and Number Theory.

Q1. 
House Robber Problem Statement
Mr. X is a professional robber with a plan to rob houses arranged in a circular street. Each house has a certain amount of money hidden, separated by a security system that ...read more
Ans. 
House Robber problem where a robber wants to maximize stolen money without robbing adjacent houses in a circular street.
• Use dynamic programming to keep track of maximum stolen money at each house.

• Consider two cases: either rob the current house and skip the next, or skip the current house.

• Handle circular arrangement by considering the first and last houses separately.

• Example: For arr[] = {2, 3, 2}, the output is 3. Rob...read more
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Q2. 
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
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Round duration - 50 Minutes
Round difficulty - Medium

Standard Data Structures and Algorithms round where I was given 2 questions to solve , one was from Linked List and the other was related to Priority Queue / Quick Sort .

Q1. 
Intersection of Linked Lists Problem Statement
You are provided with two linked lists, L1 and L2, both sorted in ascending order. Generate a new linked list containing elements that exist in both linked l...read more
Ans. 
Given two sorted linked lists, find the intersection of elements in both lists and return a new sorted linked list.
• Traverse both linked lists simultaneously to find common elements

• Create a new linked list to store the intersecting elements

• Ensure the final linked list is sorted in ascending order

• Handle cases where there are no common elements between the lists
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Q2. 
Kth Largest Element Problem Statement
Ninja enjoys working with numbers, and Alice challenges him to find the Kth largest value from a given list of numbers.
Input:
The first line contains an integer 'T...read more
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Round duration - 50 Minutes
Round difficulty - Easy

This round majorly focused on Real life appications of Data Structures and also revolved around Object Oriented Programming Style of writing code .

Q1. 
Data Structure with Insert, Delete, and GetRandom Operations
Design a data structure that supports four operations: insert an element, remove an element, search for an element, and get a random element. E...read more
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Q2. 
LRU Cache Design Question
Design a data structure for a Least Recently Used (LRU) cache that supports the following operations:
1. get(key) - Return the value of the key if it exists in the cache; otherw...read more
Ans. 
Design a Least Recently Used (LRU) cache data structure that supports get and put operations with capacity constraint.
• Implement a doubly linked list to maintain the order of keys based on their recent usage.

• Use a hashmap to store key-value pairs for quick access.

• When capacity is reached, evict the least recently used item before inserting a new item.

• Update the position of a key in the linked list whenever it is accesse...read more
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Round duration - 45 Minutes
Round difficulty - Medium

This round was inclined towards some Low Level Design Principles and some concepts from Java .

Q1. Design a Railway Reservation System.
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Q2. Why is Java considered platform-independent while the Java Virtual Machine (JVM) is platform-dependent?
Ans. 
Java is platform-independent because the code is compiled into bytecode that can run on any platform with a JVM, which is platform-dependent due to its reliance on the underlying hardware and operating system.
• Java code is compiled into bytecode, which can run on any platform with a JVM.

• JVM acts as an interpreter that translates bytecode into machine code specific to the underlying hardware and operating system.

• The JVM ...read more
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Round duration - 90 Minutes
Round difficulty - Medium

This Round was DS and Algo round and it started with formal introduction, followed by 2 problems. We first dicussed the approach the time complexity and proper code covering all cases.

Q1. 
Minimum Cost to Buy Oranges Problem Statement
You are given a bag of capacity 'W' kg and a list 'cost' of costs for packets of oranges with different weights. Each element at the i-th position in the list...read more
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Q2. 
K - Sum Path In A Binary Tree
Given a binary tree where each node contains an integer value, and a value 'K', your task is to find all the paths in the binary tree such that the sum of the node values in ...read more
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Round duration - 40 Minutes
Round difficulty - Medium

This round majorly focused on puzzles and some questions revolving around Computer Networks and the projects in my resume .

Q1. You have two wires of different lengths that take different times to burn. How can you measure a specific amount of time using these two wires?
Ans. 
Use two wires of different lengths to measure a specific amount of time by burning them simultaneously.
• Burn both wires at the same time, one wire will burn faster than the other.

• Measure the time it takes for the faster burning wire to completely burn.

• Calculate the specific amount of time by using the ratio of the lengths of the two wires.
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Q2. You have 3 ants located at the corners of a triangle. The challenge is to determine the movement pattern of the ants if they all start moving towards each other. What will be the outcome?
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Round duration - 30 Minutes
Round difficulty - Easy

This is a cultural fitment testing round .HR was very frank and asked standard questions. Then we discussed about my role.

Q1. What do you know about the company?
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Q2. Why should we hire you?
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Round duration - 90 minutes
Round difficulty - Medium

Round duration - 60 minutes
Round difficulty - Medium

This was the technical round, held around at 10 AM IST on Google Meet.
Firstly she greeted me and asked me to tell something about myself, to which I introduced myself, explaining my academic and some projects also.
After that we moved on to the Hackathon project, which was smart cart self-checkout system. I explained the project along with the code, wherever necessary.
Every word you say while explaining should be clear to you.I used Firebase and SQL while explaining my project, to which she asked some questions related to it, 
Then she moved to the DBMS part, types of joins,what is indexing, how to approach if you were to design a payment system.
At last she asked me some Data Structure questions, which were of medium complexity

Q1. 
Remove the Kth Node from the End of a Linked List
You are given a singly Linked List with 'N' nodes containing integer data and an integer 'K'. Your task is to delete the Kth node from the end of this Lin...read more
Ans. 
Remove the Kth node from the end of a singly linked list given the position 'K'.
• Traverse the list to find the length 'N' of the linked list.

• Calculate the position of the node to be removed from the beginning as 'N - K + 1'.

• Traverse the list again and remove the node at the calculated position.
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Q2. 
House Robber Problem Statement
Consider Mr. X, a professional robber who is planning to rob houses along a street. These houses are arranged in a circle, which means the first house is a neighbor to the l...read more
Ans. 
House Robber problem where adjacent houses have connected security system, find maximum money Mr. X can rob without triggering security.
• Use dynamic programming to keep track of maximum money robbed at each house.

• At each house, decide whether to rob the current house or skip it based on maximum money robbed so far.

• Handle the circular nature of houses by considering two cases: robbing the first house and not robbing the ...read more
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Round duration - 30 minutes
Round difficulty - Easy

The interviewer was very frank and cheerful. This was held at 2:30 PM IST on Google Meet.
He firstly greeted me and asked me how I was doing.
How was my previous round, any technical difficulties?
Then he asked me to introduce myself.
He started telling about his journey to Lowe's and his technical background.
Then he asked some HR related questions

2 DSA questions and some MCQ on Java and Spring

Q1. Longest palindromic substring
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Q2. Remove duplicates in place from a 1D array
Ans. 
Remove duplicates from a 1D array of strings in place
• Iterate through the array and use a HashSet to keep track of unique elements

• Replace duplicates with null or an empty string to remove them in place
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Q1. Project discussion
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Q2. Search min element in a rotated sorted array with duplicate elements
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Q3. Ways of declaring singleton class
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Q1. Project discussion
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Q2. Behavioural questions
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Q1. Why string arr immutable
Ans. 
String arrays are immutable because they cannot be changed once created.
• Strings in an array cannot be modified individually

• Any changes to a string array result in a new array being created

• Immutable arrays ensure data integrity and prevent unintended side effects
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Q2. How we can create a custom immutable class
Ans. 
To create a custom immutable class, use final keyword for class, private final fields, and no setter methods.
• Use the final keyword for the class to prevent inheritance

• Declare all fields as private and final to prevent modification

• Do not provide setter methods for the fields to maintain immutability

• Provide getter methods to access the fields
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