Lenskart SDE-2 Interview Questions and Answers

Round duration - 1hour
Round difficulty - Hard

Q1. 
Snake and Ladder Problem Statement
Given a 'Snake and Ladder' board with N rows and N columns, where positions are numbered from 1 to (N*N) starting from the bottom left, alternating direction each row, f...read more
Ans. 
Find the minimum number of dice throws required to reach the last cell on a 'Snake and Ladder' board.
• Use Breadth First Search (BFS) algorithm to find the shortest path from start to end cell.

• Keep track of visited cells and the number of dice throws required to reach each cell.

• Consider the presence of snakes and ladders while calculating the next possible moves.

• Return the minimum number of dice throws to reach the last
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Round duration - 1hour
Round difficulty - Hard

Q1.  Stack using queue
Mvvm architecture
Ans. 
Implement a stack using a queue in MVVM architecture
• Use two queues to simulate a stack

• Push operation: Enqueue the element to queue 1

• Pop operation: Dequeue all elements from queue 1 to queue 2, dequeue the last element from queue 2 (which is the top of the stack)

• Ensure proper synchronization between the two queues

• Example: Push(1), Push(2), Pop() should return 2
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Round duration - 1hour
Round difficulty - Easy

Round duration - 60 minutes
Round difficulty - Easy

Timing: evening
Environment: Online round took at home

Q1. 
Smallest Subarray with K Distinct Elements Problem
Given an array A consisting of N integers, find the smallest subarray of A that contains exactly K distinct integers.
Input:
The first line contains tw...read more
Ans. 
Find the smallest subarray with exactly K distinct integers in an array.
• Use a sliding window approach to keep track of the subarray with K distinct integers.

• Use a hashmap to store the frequency of each integer in the current window.

• Update the window size based on the number of distinct integers found.

• Keep track of the smallest subarray meeting the criteria.

• Return the starting and ending indices of the smallest subarray
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Round duration - 90 minutes
Round difficulty - Medium

Machine coding round

Round duration - 60 minutes
Round difficulty - Medium

Q1. 
Rat In a Maze Problem Statement
Given a N * N maze with a rat placed at position MAZE[0][0], find and print all possible paths for the rat to reach its destination at MAZE[N-1][N-1]. The rat is allowed to...read more
Ans. 
The problem involves finding all possible paths for a rat to reach its destination in a maze.
• Use backtracking to explore all possible paths in the maze.

• Mark visited cells to avoid revisiting them.

• Return the path once the destination is reached.

• Handle edge cases like blocked cells and out-of-bounds movements.
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Round duration - 60-90 minutes
Round difficulty - Medium

Round duration - 60 minutes
Round difficulty - Medium

Hiring Manager round

2 Coding questions both easy-medium level.
1. Based on the Sliding Window
2. Graph Question

A simple feed platform, which supports some basic functionality. The main point of this round was to see how well a candidate architect the application.

Q1. Basic discussion around the project & past experience.
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Q2. Design a 2/3rd Winning game.
Ans. 
Design a 2/3rd Winning game.
• The game should have a clear win condition

• The win condition should be achievable in 2/3rd of the total game time

• The game should have a balanced difficulty level

• The game should have a clear feedback system for the player

• Examples: Chess, Tic Tac Toe, Connect Four
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Q3. Discussion around how would you scale a application.
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Q4. NoSQL vs SQL difference
Ans. 
NoSQL is non-relational and schema-less while SQL is relational and has a fixed schema.
• NoSQL databases are horizontally scalable and can handle large amounts of unstructured data.

• SQL databases are vertically scalable and are better suited for structured data with complex relationships.

• NoSQL databases are often used in web applications, while SQL databases are commonly used in enterprise applications.

• Examples of NoSQL d...read more
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Q1. Hiring Manager round
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Q2. Basic discussions around past work, past processes, what are your future aspirations etc.
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Q3. This round was mainly for seeing the culture fitment of a candidate.
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Round duration - 120 minutes
Round difficulty - Medium

it was morning 10AM-12
friendly environment given by the interviewer
It was machine coding round, the problem statement was to create a online food ordering system with various features.
interviewer was good and supportive

Round duration - 60 Minutes
Round difficulty - Medium

timing noon 3-4Pm
good interviewer 
interviwer was giving hints if required and all

Q1. 
Problem: Sort an Array of 0s, 1s, and 2s
Given an array/list ARR consisting of integers where each element is either 0, 1, or 2, your task is to sort this array in increasing order.
Input:
The input sta...read more
Ans. 
Sort an array of 0s, 1s, and 2s in increasing order.
• Use a three-pointer approach to sort the array in a single pass.

• Initialize three pointers for 0, 1, and 2 values and iterate through the array.

• Swap elements based on the values encountered to achieve the sorted array.

• Example: Input array [0, 2, 1, 1] should be sorted as [0, 1, 1, 2].
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Q2. 
Maximum Path Sum Problem Statement
You are given an n-ary tree consisting of 'N' nodes. Your task is to determine the maximum sum of the path from the root to any leaf node.
Example:
Input:
For the giv...read more
Ans. 
Find the maximum sum of the path from the root to any leaf node in an n-ary tree.
• Traverse the tree from root to leaf nodes, keeping track of the sum along the path.

• At each node, calculate the sum of the path from the root to that node and update the maximum sum found so far.

• Consider using depth-first search (DFS) to traverse the tree efficiently.

• Handle cases where nodes are absent (-1) by appropriately updating the pat...read more
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Round duration - 90 Minutes
Round difficulty - Easy

evening 4-5:30PM
interviewer was good
very supportive and giving hints

Q1. Design a system for BookMyShow to allow users to book movie tickets.
Ans. 
Design a system for BookMyShow to allow users to book movie tickets.
• Create a user-friendly website and mobile app for users to browse movies and showtimes.

• Implement a secure payment gateway for users to purchase tickets online.

• Develop a database to store movie information, showtimes, and user bookings.

• Include features like seat selection, ticket confirmation, and booking history for users.

• Integrate with cinema partners
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Round duration - 40 Minutes
Round difficulty - Easy

4-5 PM
Interviewer was good

Q1. Why should we hire you?
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Q2. Why are you considering a switch in your job?
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This was a machine coding round in which we have to implement an online cab booking service.

Standard problem solving round consists of two questions on tree and dp.

That is machine coding round, where one problem will be given and you have to implement proper functionality with correct test cases.