Westin Full Stack Developer Interview Questions and Answers

DSA , medium n easy leetcode question was there

Q1. Low level design
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Q2. DSA and computer fundamental
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Q1. Dictionary Sort , DFS, BFS
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Q1. Reverse a LinkedList from m to n
Ans. 
Reverse a LinkedList from m to n
• Traverse the list to m-1th node

• Reverse the nodes from m to n

• Connect the reversed list to the original list
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3 coding questions and platform was hackerrank

Q1. Some medium Graph problems from leetcode
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3 coding questions and platform was hackerrank

Q1. Two medium graph questions from leetcode
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Q1. Operating system questions
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Linked list standard questions

Round duration - 90 Minutes
Round difficulty - Easy

This round was conducted on the HackerEarth platform. It had 2 sections and candidates were given a time of 1 hour 30 minutes. 

Programming MCQs — 18 MCQs (each of 2 marks)
Questions were a little tricky. it tested upon one’s programming fundamentals. It had C/C++ output questions, pseudocode questions, Operating systems, and SQL queries.
Coding — 2 ( one contains 75 marks and the other contains 100 marks )

Our scores of the first 2 sections weren’t revealed. My MCQs went really well. I solved 2 coding questions in the coding section. Only 15 students got selected for the interview round, and I was one of them.

Q1. 
Count Ways to Complete Journey in Triangular Pyramid
Given a triangular pyramid with vertices marked as ‘O’, ‘X’, ‘Y’, and ‘Z’, and an integer 'N', you need to calculate the number of ways Bob can start a...read more
Ans. 
Calculate the number of ways to complete a journey in a triangular pyramid starting and ending at a specific vertex after taking a certain number of steps.
• Use dynamic programming to calculate the number of ways to return to the starting vertex after 'N' steps.

• Consider the possible movements from each vertex to adjacent vertices.

• Keep track of the number of ways to reach each vertex after each step.

• Return the total numbe...read more
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Q2. 
Maximum Profit Problem Statement
Mukesh is evaluating the maximum profit from his business over a series of days. Given a list of profits over 'N' days, Mukesh wants to determine the highest profit achiev...read more
Ans. 
The task is to find the maximum profit achievable over any consecutive days within a specified range {‘A’, ‘B’}.
• Iterate through the profit array and calculate the cumulative sum for each possible consecutive days within the range {‘A’, ‘B’}.

• Keep track of the maximum profit obtained during the iteration.

• Return the maximum profit as the final result.
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Round duration - 60 Minutes
Round difficulty - Medium

This round was scheduled for 1 hour and the panel had 1 interviewer. Being a virtual interview, the first challenge that I faced was that the interviewer was not audible. I suggest you not panic in such a situation and use the chatbox feature (or contact HR if need be) to figure out something that works for you and the panel. We later connected over voice call (over the phone) with our videos ON (over a laptop) and continued with the interview.

The interview was very calm and helpful. I was able to solve all questions and I explained different approaches to solve the questions. Once he was convinced of my solution, he asked me to write the code on my own IDE.

Q1. 
Running Median Problem
Given a stream of integers, calculate and print the median after each new integer is added to the stream.
Output only the integer part of the median.
Example:
Input:
N = 5  
Stre...read more
Ans. 
Calculate and print the median after each new integer is added to the stream.
• Use a min heap to store the larger half of the numbers and a max heap to store the smaller half

• Keep the sizes of the two heaps balanced to efficiently calculate the median

• If the total number of elements is odd, the median will be the top element of the max heap

• If the total number of elements is even, the median will be the average of the top e
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Q2. 
Boundary Traversal of a Binary Tree
Given a binary tree of integers, your task is to return the boundary nodes of the tree in Anti-Clockwise direction starting from the root node.
Input:
The first line ...read more
Ans. 
Return the boundary nodes of a binary tree in Anti-Clockwise direction starting from the root node.
• Traverse the left boundary nodes in a top-down manner

• Traverse the leaf nodes from left to right

• Traverse the right boundary nodes in a bottom-up manner

• Handle cases where duplicates occur in the boundary nodes

• Implement the function without printing as printing is already managed
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Q3. 
Count Pairs with Given Sum
Given an integer array/list arr and an integer 'Sum', determine the total number of unique pairs in the array whose elements sum up to the given 'Sum'.
Input:
The first line c...read more
Ans. 
Count the total number of unique pairs in an array whose elements sum up to a given value.
• Use a hashmap to store the frequency of each element in the array.

• Iterate through the array and for each element, check if (Sum - current element) exists in the hashmap.

• Increment the count of pairs if the complement exists in the hashmap.
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Round duration - 90 Minutes
Round difficulty - Medium

This was a technical + HR round. First, he asked me to introduce myself. This round was also based on your knowledge of DSA. I was asked 2 coding questions. Then he asked a couple of questions from OS and DBMS which were pretty easy. At last, we ended the interview on a good note. Then he asked me questions about myself.
Why I want to join OYO rooms. 
What are my hobbies?
Goals in the next five years.

Q1. 
Zig-Zag String Problem Statement
Given a string 'STR' of length 'N' and an integer 'M' representing the number of rows in the zig-zag pattern, your task is to return the string formed by concatenating all...read more
Ans. 
Given a string and number of rows, return the concatenated string formed by arranging the input string in a zig-zag pattern over the specified number of rows.
• Iterate through the string and distribute characters in zig-zag pattern over 'M' rows

• Keep track of the direction of movement (up or down) while distributing characters

• Concatenate characters row-wise to get the final zig-zag pattern string
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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 find the total number of ways to make change for a specified value using given denominations.
• Use dynamic programming to solve this problem efficiently.

• Create a 2D array to store the number of ways to make change for each value using different denominations.

• Iterate through the denominations and update the array accordingly.

• The final answer will be stored in the last cell of the array.

• Consider edge cases l
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Round duration - 90 Minutes
Round difficulty - Hard

Timing was 11 am. Platform was quite well.

Q1. 
Rat in a Maze Problem Statement
You need to determine all possible paths for a rat starting at position (0, 0) in a square maze to reach its destination at (N-1, N-1). The maze is represented as an N*N ma...read more
Ans. 
Find all possible paths for a rat in a maze from source to destination.
• Use backtracking to explore all possible paths in the maze.

• Keep track of visited cells to avoid revisiting them.

• Explore all possible directions (up, down, left, right) from each cell.

• Add the current direction to the path and recursively explore further.

• When reaching the destination, add the path to the list of valid paths.
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Q2. 
Minimum Cost to Destination
You are given an NxM matrix consisting of '0's and '1's. A '1' signifies that the cell is accessible, whereas a '0' indicates that the cell is blocked. Your task is to compute ...read more
Ans. 
Find the minimum cost to reach a destination in a matrix with blocked cells.
• Use Breadth First Search (BFS) algorithm to explore all possible paths from the starting point to the destination.

• Keep track of the cost incurred at each cell and update it as you move through the matrix.

• Return the minimum cost to reach the destination or -1 if it is unreachable.

• Consider edge cases such as when the starting point is the destina
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Round duration - 90 minutes
Round difficulty - Medium

Q1. 
Rotate Matrix Right K Times
You are given a matrix MAT of size 'N' * 'M', where 'N' is the number of rows and 'M' is the number of columns, along with a positive integer 'K'. Your task is to rotate the ma...read more
Ans. 
Rotate a matrix to the right 'K' times by shifting each column to the right 'K' times.
• Iterate 'K' times to perform right rotation on the matrix

• Shift each column to the right by one position in each rotation

• Handle wrapping around the matrix when shifting columns

• Return the matrix elements row-wise after 'K' rotations
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Q2. 
Word Search Problem Statement
Given a two-dimensional grid of size N x M consisting of upper case characters and a string 'WORD', determine how many times the 'WORD' appears in the grid.
The 'WORD' can b...read more
Ans. 
Count how many times a given word appears in a 2D grid by moving in any of the eight possible directions.
• Iterate through each cell in the grid and check if the word can be formed starting from that cell in any of the eight directions.

• Use recursion to explore all possible paths from a starting cell to form the word.

• Keep track of visited cells to avoid revisiting the same cell in the same path.

• Return the count of how man
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Round duration - 75 minutes
Round difficulty - Medium

Interview started with an introduction and walk through the resume for first 5 minutes. After that, interview asked few coding questions.

Q1. 
Problem Statement: Largest Island
You are provided with a non-empty grid consisting of only 0s and 1s. Your task is to determine the maximum area of an island within the given grid.
An island consists of a...read more
Ans. 
Find the maximum area of an island in a grid of 0s and 1s.
• Iterate through the grid and perform depth-first search (DFS) to find connected 1s.

• Keep track of the area of each island found and return the maximum area.

• Consider all four directions (horizontal, vertical, and diagonal) while exploring the island.

• Handle edge cases like grid boundaries and already visited cells during DFS.

• If no island is present, return 0 as the
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Q2. 
Pythagorean Triplet Problem
Determine if there exists a Pythagorean triplet within a given array of integers. A Pythagorean triplet consists of three numbers, x, y, and z, such that x^2 + y^2 = z^2.
Expl...read more
Ans. 
Check if there exists a Pythagorean triplet in a given array of integers.
• Iterate through all possible triplets in the array and check if they form a Pythagorean triplet.

• Use a nested loop to generate all possible combinations of three numbers from the array.

• Check if the sum of squares of two numbers is equal to the square of the third number.
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Q3. 
Top View of Binary Tree Problem Statement
Given a Binary Tree of integers, you are tasked with finding the top view of the binary tree. The top view is the set of nodes visible when the tree is viewed fro...read more
Ans. 
Find the top view of a Binary Tree by returning a list of visible nodes when viewed from the top.
• Traverse the Binary Tree in level order and keep track of the horizontal distance of each node from the root.

• Use a map to store the nodes at each horizontal distance, and only keep the topmost node for each horizontal distance.

• Return the values of the topmost nodes in the map as the top view of the Binary Tree.
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Round duration - 90 minutes
Round difficulty - Medium

This round was focused on DSA along with short discussion on computer science fundamentals. For coding problems, I was asked to code the first problem only. For others, had to discuss the approach only. For computer science fundamentals, discussion on OOPS. Differences between process and threads were discussed.

Q1. 
Fixing a Swapped Binary Search Tree
Given a Binary Search Tree (BST) where two nodes have been swapped by mistake, your task is to restore or fix the BST without changing its structure.
Input:
The first...read more
Ans. 
Restore a Binary Search Tree by fixing two swapped nodes without changing its structure.
• Identify the two nodes that are swapped by mistake in the BST.

• Swap the values of the two identified nodes to restore the BST.

• Perform an in-order traversal of the BST to verify the correct restoration.

• Ensure no extra space other than the recursion stack is used for the solution.
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Q2. 
Implement Stack with Linked List
Your task is to implement a Stack data structure using a Singly Linked List.
Explanation:
Create a class named Stack which supports the following operations, each in O(1...read more
Ans. 
Implement a Stack data structure using a Singly Linked List with operations like getSize, isEmpty, push, pop, and getTop in O(1) time.
• Create a class named Stack with methods for getSize, isEmpty, push, pop, and getTop.

• Use a Singly Linked List to store the elements of the stack.

• Ensure that each operation runs in constant time O(1).

• Handle edge cases like empty stack appropriately.

• Test the implementation with sample queri
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Round duration - 90 Minutes
Round difficulty - Easy

Q1. 
Position of Right Most Set Bit
Determine the position of the rightmost set bit in the binary representation of a given number N.
Input:
T: Number of test cases
N: An integer for which the position of the...read more
Ans. 
Find the position of the rightmost set bit in a given number's binary representation.
• Convert the number to binary representation.

• Find the position of the rightmost set bit by counting from right to left.

• Return the position of the rightmost set bit.
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Round duration - 60 Minutes
Round difficulty - Medium

Q1. 
Water Jug Problem Statement
You have two water jugs with capacities X and Y liters respectively, both initially empty. You also have an infinite water supply. The goal is to determine if it is possible to...read more
Ans. 
The Water Jug Problem involves determining if a specific amount of water can be measured using two jugs of different capacities.
• Start by considering the constraints and limitations of the problem.

• Think about how the operations allowed can be used to reach the target measurement.

• Consider different scenarios and test cases to understand the problem better.

• Implement a function that can determine if the target measurement
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Round duration - 60 Minutes
Round difficulty - Medium