Xeno Interview Questions and Answers

Easy basic dsa questions

Q1. Basics of dsa and project discussion
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Q2. Stair climbing based on dp
Ans. 
Dynamic programming approach to solve the stair climbing problem efficiently.
• Define the problem: Given n stairs, find the number of ways to reach the top.

• Base cases: If n = 0, return 1; if n = 1, return 1.

• Recurrence relation: ways(n) = ways(n-1) + ways(n-2).

• Use an array to store results of subproblems to avoid recomputation.

• Example: For n = 4, ways(4) = ways(3) + ways(2) = 3 + 2 = 5.
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Q3. Longest common subsequence
Ans. 
Longest common subsequence is the longest sequence of characters that appear in the same order in two or more strings.
• Use dynamic programming to solve this problem efficiently.

• Create a 2D array to store the lengths of longest common subsequences of substrings.

• Traverse the array to find the longest common subsequence.
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Q4. Buy and sell stock
Ans. 
Determine the best time to buy and sell stock to maximize profit from given price data.
• Identify the lowest price to buy before a higher price to sell.

• Track price changes over time to find optimal buy/sell points.

• Example: Prices = [7, 1, 5, 3, 6, 4]; Buy at 1, sell at 6 for max profit of 5.

• Consider edge cases: prices always decreasing means no profit can be made.
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Q5. Project discussion based on resume
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Q1. 2 sum problem [leetcode]
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Q2. Linkedlist problem
Ans. 
Implement various operations on a linked list and solve related problems like reversing a linked list or detecting a cycle.
• Understand the basic structure of a linked list with nodes containing data and a reference to the next node.

• For insertion, update the pointers of the nodes accordingly to maintain the sequence.

• For deletion, adjust the pointers to skip the node to be deleted.

• To reverse a linked list, iterate through...read more
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Q1. Given a data set of hotel you need to find number of booking.
Ans. 
Calculate the number of hotel bookings from a given dataset of hotels and their booking details.
• Identify the data structure: Ensure the dataset contains booking information, such as hotel ID, customer ID, and booking dates.

• Count unique bookings: Use a method to count unique entries based on hotel ID and booking dates to avoid duplicates.

• Example: If hotel A has 3 bookings on different dates and hotel B has 2 bookings, t...read more
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Q2. SQL Query based upon join leetcode.
Ans. 
SQL joins combine rows from two or more tables based on related columns, essential for relational database queries.
• INNER JOIN: Returns records with matching values in both tables. Example: SELECT * FROM A INNER JOIN B ON A.id = B.a_id;

• LEFT JOIN: Returns all records from the left table and matched records from the right table. Example: SELECT * FROM A LEFT JOIN B ON A.id = B.a_id;

• RIGHT JOIN: Returns all records from the...read more
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He will be asking you about the logic you used to solve the OA questions. So prepare well.
He then asked questions from my resume and asked me to code and explain cycle in a linked list. I easily did the coding part using brute force and optimized approach but then he asked my to give proof that why tortoise and hare algo will work here. I explained him the mathematical proof.

Q1. In this round he started asking questions from my resume and then gave me DSA question to solve which was 523. Continuous subarray sum and then he asked me several question related to Reactjs , Nodejs , Mo...read more
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Q2. 523. Continuous Subarray sum
Ans. 
Determine if a continuous subarray sums to a multiple of k.
• A continuous subarray is defined as a sequence of elements from the array.

• The sum of the subarray must be a multiple of k (i.e., sum % k == 0).

• Example: For nums = [23, 2, 4, 6, 7] and k = 6, the subarray [2, 4] sums to 6, which is a multiple of 6.

• Use a hashmap to store the cumulative sum and its index to check for previous occurrences.

• If the same cumulative sum...read more
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