Round: Full Journey · Type: Multiple Types · Difficulty: 5/10 · Duration: 180 min · Interviewer: Unfriendly
Topics: System Design, Binary Tree, Intervals, Algorithms
Location: Menlo Park, CA
Interview date: 2026-01-04
Summary
Round 1: Phone Screen
Question: How many extra parentheses are needed to balance an expression, and find the lowest common ancestor for two nodes in a binary tree, given parent pointers.
Round 2: Onsite System Design
Question: Design a News Feed feature, including comment and like functionality.
Round 3: Onsite Coding
Question: Implement a calculator that supports addition, multiplication, and exponentiation, and merge two sorted intervals.
Details
Preparation Tips & Key Takeaways
What I Learned
I learned the importance of understanding the underlying data structures when solving tree-based problems.
I also realized the importance of clearly defining the scope and constraints of a system design problem before diving into the implementation details.
Recommended Preparation
Coding Practice
Practice binary tree traversals and related algorithms.
Review interval merging problems and calculator implementations.
System Design
Study common system design patterns, such as caching and load balancing.