As a final-year student, I had the amazing opportunity to interview with OYO Rooms for a 6-month Software Development Internship. The process tested not only my problem-solving skills but also my computer science fundamentals. You can also read about my work during the internship in this article.

Here’s a detailed breakdown of my interview journey 👇

💡 Round 1: Online Coding Test (HackerEarth)

Format: 3 DSA problems | Duration: 1.5 hours 🚀

The questions in my OA were essentially variations of these problems. If you practice them beforehand then you’ll gain the right intuition .

1. DP Problem 1: A standard subsequence variation — Longest Increasing Subsequence.
   👉 LeetCode 300 — Longest Increasing Subsequence
2. DP Problem 2: A grid-based DP requiring state management with optimized transitions — Cherry Pickup II.
   👉 LeetCode 1463 — Cherry Pickup II
3. Trie Problem: A prefix-based string problem involving efficient lookups — Replace Words.
   👉 LeetCode 648 — Replace Words

➡️ This round mainly tested speed + accuracy with medium-to-hard level problems.

💡 Round 2: Technical Interview (DSA Focus)

This round was a one-on-one technical interview (F2F), entirely focused on data structures and algorithms (Medium level).🚀

1. ◼️ Doubly Linked List — Sum of Pairs Problem:

• Problem: Given a doubly linked list and a target sum, determine if there exists a pair of nodes whose values add up to the target.
• Challenge: Since a doubly linked list allows traversal from both ends, the optimal solution leverages two pointers, starting from the head and tail, moving inward to find the sum.
• Edge Cases: Handling empty lists, single-node lists, duplicate values, and negative numbers.
• Reference: Find pairs with given sum in DLL — GeeksforGeeks🌐

2. ◼️ Binary Search Tree — Kth Largest and Kth Smallest Element:

• Problem: Given a BST and an integer k, find the kth smallest and kth largest elements.
• Challenge: Utilize the in-order traversal (which gives sorted order) for the kth smallest and reverse in-order traversal for the kth largest. Efficiently tracking count during traversal is key.
• Edge Cases: Handling trees with fewer than k nodes, duplicate values, and unbalanced trees.
• Reference: Kth largest/smallest in BST — Take U Forward🌐

💡 Round 3: Technical Interview (DSA + CS Fundamentals)

This was the most challenging round, mixing both advanced DSA and core CS concepts.

1. ◼️ Topological Sort Problem: Vehicle Assembly Line

Scenario:
Imagine you’re tasked with assembling a vehicle from various parts where certain parts must be assembled before others. Determine if it’s possible to assemble the vehicle by placing the parts in the correct order or not.

📌Problem Breakdown:

• Input: A directed acyclic graph (DAG) where nodes = parts, edges = assembly order.
• Output: Topological ordering or detect cycle.

📝Key Concepts:

• Topological Sorting: The process of ordering vertices in a DAG such that for every directed edge u → v, vertex u comes before v in the ordering.
• Cycle Detection: Ensuring the graph is acyclic is crucial; the presence of a cycle makes topological sorting impossible.

📚Resources:

• TUF: Kahn’s Algorithm🌐
• GeeksforGeeks: Topological Sorting🌐

2. ◼️ Dynamic Programming (DP) Grid Problem: Counting Paths

Scenario:
Count distinct paths in a 2D grid with blocked/open cells, moving only right or down.

📌Problem Breakdown:

• Input: A 2D grid where each cell is either open (0) or blocked (-1).
• Output: The total number of distinct paths from the top-left to the bottom-right corner.

📝Approach:

• Dynamic Programming (DP): Use a 2D DP array where each cell dp[i][j] represents the number of ways to reach that cell from the top-left corner.
• Transition: For each open cell, the number of ways to reach it is the sum of the ways to reach the cell directly above it and the cell directly to its left.

📚Resources:

• Take U Forward: DP on Grids🌐
• Unique Grids Path 2🌐

🖥️ CS Fundamentals Questions

Difference between SQL and NoSQL databases

Difference between Semaphore and Mutex

Explain how a website works (including DNS, frontend and backend integration)

Types of Polymorphism (Early binding vs Late binding)

Multithreading and its advantages

What are various HTTP verbs

Difference between DELETE and DROP commands

👉 Verdict : Selected for the internship!🎯🚀

💡 Key Takeaways

1. DSA is king 👑 → Most of the rounds focused on data structures and algorithms. Practice standard patterns (DP, Graphs, Trees, Linked Lists, Arrays).
2. CS fundamentals matter → OS, DBMS, and Networking basics were tested.
3. Problem framing is important → The topological sort problem was disguised as a real-world scenario (vehicle parts assembly).
4. Clarity > Syntax → Explaining thought process clearly was more important than perfect syntax.
5. Helpful resources :

• Striver’s A-Z DSA Sheet 🌐
• Frequent interview questions in Operating Systems (OS), Object-Oriented Programming (OOP), and Database Management Systems (DBMS)🌐

✨ Final Thoughts

For anyone preparing for OYO or other product-based companies, focus on DSA, strengthen your CS fundamentals, and practice explaining solutions clearly, step by step.

Written by Shhreyyyaa