Wayfair Software Engineer III Interview Questions and Answers

Q1. Delete nth node from end in linked list
Ans. 
To delete the nth node from the end in a linked list, we can use a two-pointer approach.
• Use two pointers, one to traverse the list and another to keep track of the nth node from the end.

• Move the second pointer n steps ahead of the first pointer.

• When the second pointer reaches the end of the list, the first pointer will be at the nth node from the end.

• Adjust the pointers to delete the nth node.
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Q2. Project discussion
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4 questions , 3 DSA questions medium level and 1 DB design round

Q1. Questions on OOPs, Networking, OS app development, projects and DSA questions
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Q1. DB related questions (joins,query) and Linked list medium DSA question.
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The coding test was divided in 4 sections:
1> Java and SpringBoot multiple choice questions
The question topics included, multihreading, springboot context, security

2> Leetcode style program question 1 - Easy

3> Leetcode style program question 2 - Medium
Length of longest consecutive ones by at most one swap.

4> Sql query question

Round duration - 90 minutes
Round difficulty - Medium

This round had 3 coding questions of Medium to Hard level of difficulty.

Q1. 
Intersection of Two Unsorted Arrays Problem Statement
Given two integer arrays ARR1 and ARR2 of sizes 'N' and 'M' respectively, find the intersection of these arrays. The intersection is defined as the se...read more
Ans. 
Find the intersection of two unsorted arrays while maintaining the order of elements from the first array.
• Iterate through the elements of the first array and check if they exist in the second array.

• Use a hash set to keep track of elements already seen in the second array for efficient lookup.

• Maintain the order of elements from the first array while finding the intersection.

• Handle duplicate elements in both arrays appro...read more
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Q2. 
Ways To Make Coin Change
Given an infinite supply of coins of varying denominations, determine the total number of ways to make change for a specified value using these coins. If it's not possible to make...read more
Ans. 
The task is to determine the total number of ways to make change for a specified value using given denominations.
• Create a function that takes in the number of denominations, the denominations array, and the value to make change for as input

• Use dynamic programming to iterate through all possible combinations of coins to make the specified value

• Keep track of the number of ways to make change for each value from 0 to the ...read more
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Q3. 
Longest Substring Without Repeating Characters Problem Statement
Given a string S of length L, determine the length of the longest substring that contains no repeating characters.
Example:
Input:
"abac...read more
Ans. 
Find the length of the longest substring without repeating characters in a given string.
• Use a sliding window approach to keep track of the longest substring without repeating characters.

• Use a hashmap to store the index of each character in the string.

• Update the start index of the window when a repeating character is encountered.

• Calculate the maximum length of the substring as you iterate through the string.
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Round duration - 60 minutes
Round difficulty - Medium

This round started with 2 coding questions and then moved on to some more questions from OOPS.

Q1. 
Palindrome Linked List Problem Statement
You are provided with a singly linked list of integers. Your task is to determine whether the given singly linked list is a palindrome. Return true if it is a pali...read more
Ans. 
Check if a given singly linked list is a palindrome or not.
• Traverse the linked list to find the middle element using slow and fast pointers.

• Reverse the second half of the linked list.

• Compare the first half with the reversed second half to determine if it's a palindrome.
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Q2. 
Search Element in a Rotated Sorted Array
Given a sorted array that has been rotated, the task is to find the index of a specific element. The array is initially sorted in ascending order and then rotated ...read more
Ans. 
Search for an element in a rotated sorted array efficiently in O(logN) time complexity.
• Implement binary search to find the pivot point where rotation occurs.

• Divide the array into two subarrays and perform binary search on the appropriate subarray.

• Handle cases where the element may be in the left or right subarray after rotation.

• Return the index of the element if found, else return -1.
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Q3. What is a static variable in C?
Ans. 
A static variable in C is a variable that retains its value between function calls.
• Declared using the 'static' keyword

• Retains its value throughout the program's execution

• Useful for maintaining state across function calls
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Q4. What is the difference between abstraction and inheritance?
Ans. 
Abstraction is hiding the implementation details while inheritance is a mechanism for creating new classes using existing classes.
• Abstraction focuses on hiding the internal implementation details of a class, allowing the user to only interact with the necessary information.

• Inheritance allows a class to inherit properties and behavior from another class, promoting code reusability and creating a hierarchy of classes.

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

This round had questions mainly from HTML,CSS and JavaScript as I had mentioned some Frontend Projects in my resume so the interviewer wanted to check my skills on those. He also asked me some SQL queries and a simple coding question towards the end of the interview.

Q1. What is event bubbling in JavaScript?
Ans. 
Event bubbling is the process where an event triggered on a child element is propagated up through its parent elements.
• In event bubbling, when an event occurs on a child element, it first runs the event handlers on the child element, then on its parent, then all the way up to the top level of the DOM.

• Event bubbling allows for delegation of event handling to a parent element, reducing the number of event listeners neede...read more
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Q2. How can you optimize the loading of website assets?
Ans. 
Optimizing website asset loading involves minimizing file sizes, reducing HTTP requests, utilizing caching, and prioritizing critical resources.
• Minimize file sizes by compressing images, scripts, and stylesheets.

• Reduce HTTP requests by combining files, using sprites, and lazy loading non-essential resources.

• Utilize browser caching to store static assets locally for faster subsequent page loads.

• Prioritize critical resou...read more
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Q3. In how many ways can you display HTML elements?
Ans. 
There are multiple ways to display HTML elements, including inline, block, inline-block, and flex.
• HTML elements can be displayed as inline, which allows them to flow with surrounding content.

• Block elements take up the full width available and start on a new line.

• Inline-block elements are displayed as blocks, but flow like inline elements.

• Flexbox allows for more advanced layout options, such as aligning items and distri
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Q4. 
Check if Two Strings are Anagrams
Anagrams are words or names that can be formed by rearranging the letters of another word. For instance, 'spar' can be rearranged to form 'rasp', making them anagrams.
E...read more
Ans. 
Check if two strings are anagrams by rearranging their letters.
• Create a frequency map of characters for both strings

• Compare the frequency maps to check if they are equal

• Return True if the frequency maps are equal, else False
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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 is something about you that is not included in your resume?
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Q2. Why should we hire you?
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Round duration - 90 minutes
Round difficulty - Medium

This round had 3 coding questions of Medium to Hard level of difficulty.

Q1. 
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 recursion to generate all possible combinations of balanced parentheses.

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

• Return the valid combinations as an array of strings.
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Q2. 
Trapping Rain Water Problem Statement
You are given a long type array/list ARR of size N, representing an elevation map. The value ARR[i] denotes the elevation of the ith bar. Your task is to determine th...read more
Ans. 
Calculate the total amount of rainwater that can be trapped between given elevations in an array.
• Iterate through the array and calculate the maximum height on the left and right of each bar.

• Calculate the amount of water that can be trapped at each bar by taking the minimum of the maximum heights on the left and right.

• Sum up the trapped water at each bar to get the total trapped water for the entire array.
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Q3. 
Rotting Oranges Problem Statement
You are given a grid containing oranges where each cell of the grid can contain one of the three integer values:
• 0 - representing an empty cell
• 1 - representing a fre...read more
Ans. 
Find the minimum time required to rot all fresh oranges adjacent to rotten oranges.
• Create a queue to store the coordinates of rotten oranges and perform BFS to rot adjacent fresh oranges.

• Track the time taken to rot all fresh oranges and return -1 if not all fresh oranges can be rotten.

• Update the grid with the new state of oranges after each second.

• Handle edge cases such as empty grid or no fresh oranges present.

• Example...read more
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Round duration - 60 Minutes
Round difficulty - Medium

This was a standard DS/Algo round where I was given 2 questions to solve under 60 minutes. I was able to come up with the optimal approach for both the questions and then at the end of the interview I was also asked the famous Die Hard Water Puzzle.

Q1. 
Queue Using Stacks Implementation
Design a queue data structure following the FIFO (First In First Out) principle using only stack instances.
Explanation:
Your task is to complete predefined functions t...read more
Ans. 
Implement a queue using stacks following FIFO principle.
• Use two stacks to simulate a queue.

• For enQueue operation, push elements onto stack1.

• For deQueue operation, if stack2 is empty, pop all elements from stack1 and push onto stack2, then pop from stack2.

• For peek operation, if stack2 is empty, pop all elements from stack1 and push onto stack2, then return top of stack2.

• For isEmpty operation, check if both stack1 and st...read more
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Q2. 
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 of merged intervals by start time.
• Sort the intervals based on start time.

• Iterate through intervals and merge overlapping ones.

• Return the merged intervals in sorted order.
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Q3. You have a 3-liter jar and a 5-liter jar. How can you measure exactly 4 liters using these two jars?
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Round duration - 60 Minutes
Round difficulty - Medium

This round had 2 coding questions - first one related to Binary Tree and the second one was a simple question from Bit Manipulation. This was followed by some questions from OOPS.

Q1. 
Binary Tree Diameter Problem Statement
You are given a Binary Tree, and you need to determine the length of the diameter of the tree.
The diameter of a binary tree is the length of the longest path betwe...read more
Ans. 
The task is to find the diameter of a binary tree, which is the length of the longest path between any two end nodes in the tree.
• Traverse the tree to find the longest path between two nodes.

• Keep track of the maximum diameter found during traversal.

• The diameter may not necessarily pass through the root node.

• Consider both left and right subtrees while calculating the diameter.

• Example: For input 1 2 3 4 -1 5 6 -1 7 -1 -1
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Q2. 
Power of 2 Problem Statement
Determine if it is possible to reorder the digits of a given integer 'N' such that the resulting number is a power of two. The leading digit must not be zero.
Input:
The fir...read more
Ans. 
The problem involves determining if it is possible to reorder the digits of a given integer to form a power of 2.
• Iterate through all possible permutations of the digits of the given integer.

• Check if any of the permutations form a power of 2.

• Return 1 if a valid permutation is found, else return 0.
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Q3. What are some advantages of using Object-Oriented Programming (OOP)?
Ans. 
Advantages of OOP include code reusability, modularity, and easier maintenance.
• Code reusability: Objects can be reused in different parts of the program, reducing redundancy.

• Modularity: OOP allows for breaking down complex problems into smaller, more manageable parts.

• Easier maintenance: Changes to one part of the codebase do not necessarily affect other parts, making maintenance easier.

• Encapsulation: Data hiding and ab...read more
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Q4. What are access specifiers and what is their significance in Object-Oriented Programming?
Ans. 
Access specifiers define the level of access to class members in Object-Oriented Programming.
• Access specifiers include public, private, protected, and default

• Public members are accessible from outside the class

• Private members are only accessible within the class

• Protected members are accessible within the class and its subclasses

• Default access is when no access specifier is specified
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Round duration - 30 Minutes
Round difficulty - Easy

This was my last round and I hoped it to go good just like the other rounds. The interviewer was very straight to point
and professional. The interview lasted for 30 minutes.

Q1. Why should we hire you?
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