Oyo Rooms Software Developer Intern Interview Questions, Process, and Tips

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. Bactracking
Approach: We can start the traversal of the paths from the rat’s starting position, i.e. (0,0) keeping track of the visited cells during the traversal. We will recursively go through all the paths possible until the last index of the grid (destination) is reached, and add the path information using which the rat successfully reached the end.
 
Algorithm is as follows:
 
1. Take the starting position of th...read more
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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. Backtracking
Maintain a visited array and try to explore all the possibilities with the help of backtracking.
1. Start with (0, 0) and mark it as visited and try to move in all 4 directions.
2. Say at any point we are at (i, j) then the cost of reaching (x,y) will be the minimum of these four cases.
   1. Option 1 -  Left: cost of reaching from (i, j-1)
   2. Option 2 - Right: cost of reaching from (i, j+1)
   3. Option 3 - Up: 1 + cost of rea...read more
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Round duration - 90 minutes
Round difficulty - Easy

Q1. 
Cycle Detection in a Directed Graph
Given a directed graph, you need to determine whether or not the graph contains a cycle.
Your function should return true if there is at least one cycle in the graph; ...read more
Ans. 
I used DFS from every unvisited node. There is a cycle in a graph only if there is a back edge present in the graph.
To find the back edge to any of its ancestor keep a visited array and if there is a back edge to any visited node then there is a loop and return true.
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Q2. 
Next Permutation Problem Statement
Given a permutation of ‘N’ integers, rearrange them to generate the lexicographically next greater permutation. A sequence is a permutation if it contains all integers f...read more
Ans. 
Traverse from right and find the first item that is not following the descending order.
Swap the found character with closest greater (or smallest greater) element on right side of it.
After swapping, sort the string after the position of character found.
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Round duration - 60 minutes
Round difficulty - Easy

Q1. 
Validate BST Problem Statement
Given a binary tree with N nodes, determine whether the tree is a Binary Search Tree (BST). If it is a BST, return true; otherwise, return false.
A binary search tree (BST)...read more
Ans. 
I gave him two three approaches.
Brute force
using utility class
using in-order traversal:
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Round duration - 90 minutes
Round difficulty - Medium

The test was scheduled at 2:30 PM, IST. The test was conducted online, due to the ongoing pandemic situation. Webcam was required to be switched on during the complete duration of the test. I had solved 2/2 coding questions with all test cases successfully passing. Out of the 10 MCQ questions, I had done 6. Around 90 students sat for the online coding round, 19 were shortlisted for the interview. Those who had solved both coding questions were called for interview.

Q1. 
Candies Distribution Problem Statement
Prateek is a kindergarten teacher with a mission to distribute candies to students based on their performance. Each student must get at least one candy, and if two s...read more
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Q2. 
Problem Statement: Minimum Cost to Buy Ninja Blades
Ninja Yuki wants to purchase ninja blades at the Spring Fair in his village. Initially, he has 0 blades, and his goal is to buy 'N' blades. The merchant...read more
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Round duration - 60 minutes
Round difficulty - Medium

This was a pure DSA based round. Two questions were asked in this round. The interviewer was quite good, and helped in between.

Q1. 
First Unique Character in a Stream Problem Statement
Given a string A consisting of lowercase English letters, determine the first non-repeating character at each point in the stream of characters.
Examp...read more
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Q2. 
Boolean Matrix Transformation Challenge
Given a 2-dimensional boolean matrix mat of size N x M, your task is to modify the matrix such that if any element is 1, set its entire row and column to 1. Specifi...read more
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Round duration - 75 minutes
Round difficulty - Medium

This round was also again focused on DSA. Two interviewers were present. This round was very extensive and everything was asked in depth as well as they asked to write the codes as well for all the questions. I was also asked to explain my projects, they were based on ML. Many aspects of OOPs, POP, memory allocation was asked as well.

Q1. 
Maximum Sum of Index-Multiplied Rotations
Given an array ARR of size N, determine the maximum sum of i * ARR[i] possible through any number of rotations. Both left and right rotations are allowed, and can...read more
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Q2. 
Averages of Levels in Binary Tree Problem Statement
Given an arbitrary binary tree consisting of 'N' nodes numbered from 1 to 'N'. Each node is associated with a positive integer value. Your task is to ca...read more
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Round duration - 60 minutes
Round difficulty - Medium

Q1. 
Longest Increasing Subsequence Problem Statement
Given an array of integers with 'N' elements, determine the length of the longest subsequence where each element is greater than the previous element. This...read more
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Q2. 
Digits Decoding Problem
Ninja has a string of characters from 'A' to 'Z', encoded using their numeric values (A=1, B=2, ..., Z=26). The encoded string is given as a sequence of digits (SEQ). The task is t...read more
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Round duration - 60 minutes
Round difficulty - Medium

Q1. 
Leaves at Same Level Problem Statement
Given a binary tree with 'N' nodes, determine if all the leaf nodes are situated at the same level. Return true if all the leaf nodes are at the same level, otherwis...read more
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Q2. 
Maximum Non-Adjacent Subsequence Sum
Given an array of integers, determine the maximum sum of a subsequence without choosing adjacent elements in the original array.
Input:
The first line consists of an...read more
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Round duration - 60 minutes
Round difficulty - Medium

Q1. 
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
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Q2. What is the difference between Mutex and Semaphores?
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Q3. Given the employee and department tables, how would you find the number of employees in each department? (This question focuses on SQL Joins.)
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