Role: SDE-1
College: Not Specified
Interview Date: July 2025 (Last Updated)
Interview Type: Telephonic (coding on collabedit)
Result: Rejected
Difficulty: Medium-Hard
Rounds: 4 rounds
Topics Asked: Data Structures (Matrix, Binary Tree, Hashmap, Trie, BST), Algorithms (Stock Buy/Sell, Percentile, Missing Number in AP), System Design (File Uploader Service), OOP, Web Technologies (Web Browser Request vs Ajax), Puzzles, Project Discussion, Database concepts.
Experience:
This candidate was interviewed by OLA for an SDE-1 role and did not make it past the last round. All initial rounds were telephonic, with coding performed on collabedit.
Round 1 (35 min):
- Given a matrix with 0s and 1s, find all rows having 1s at the same position.
- In a stock market, given share prices over a week, find the best buy and sell days for maximum profit.
- Behavioral: Being a computer engineer, why did you not opt for system-side programming rather than web domain (given prior web domain experience)?
- Technical: Difference between web browser request and AJAX call request.
- Technical: Have you worked on Ruby on Rails?
Round 2:
- Given a matrix containing numbers, find all 0s and make their corresponding rows and columns 0.
- System Design: Design a File Uploader service (e.g., Dropbox, Google Drive) that allows multiple simultaneous uploads and lists the top five uploaders.
- Puzzle: An employer has a 7-unit gold bar and must give 1 unit daily for 7 days. With a magical knife that can only make two cuts, how would you cut the bar to distribute 1 unit daily?
- Print the left view of a binary tree.
Round 3:
- Discussion on Ola's work, how things like barcode products and catalogs are implemented.
- Discussion on current project, team size.
- Database/Data Structure: What data structure would you use to implement a database (candidate suggested hashmap with primary key as key and object for fields).
- Follow-up: How to find all names starting with a particular word (candidate suggested Trie).
- Follow-up: How to find students whose marks are within a specific range (candidate couldn't answer, but hint implies binary search tree with inorder traversal).
- Opportunity to ask questions.
Round 4:
- The server receives a ping every 30 seconds, which is the load average. Find the 90th percentile of the load average at any instant.
- Find the missing number in an Arithmetic Progression (AP).