Software Engineer · Full Journey · Coding

Google — Software Engineer ✅ Passed

Level: Unknown Level

Round: Full Journey · Type: Coding · Difficulty: 4/10 · Duration: 120 min · Interviewer: Neutral

Topics: Arrays, Queues, Graphs, Binary Trees, Graph Traversal

Location: Mountain View, CA

Interview date: 2026-01-20

Summary

Round 1: Coding

Question: Given an array and an offset, output the first 'offset' elements if the offset is positive, and the last 'offset' elements if negative. Follow-up: Handle the same problem when the array is a stream with hasNext() and getNext() functions.

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Round 2: Coding

Question: Given an undirected acyclic graph, determine if it is a valid binary tree and output its root. Follow-up: Given each node has a color (black or white), check if there's a valid binary tree where each level has the same color.

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Details

Round 1: Array and Stream Processing

The coding question involved manipulating an array based on a given offset. The follow-up required adapting the solution to handle an incoming stream of data using hasNext() and getNext() methods.

My Approach:

1. For the array problem, I used array slicing based on whether the offset was positive or negative.
2. For the stream follow-up, I used a queue to store the elements and maintain the required offset.

Key Insights:

• Using a queue is an efficient way to handle streaming data.
• Understanding the constraints of the problem is crucial for optimizing the solution.

Round 2: Graph and Binary Tree Validation

The coding question was to determine if a given undirected acyclic graph is a valid binary tree and, if so, to return its root. The follow-up added the constraint that each node has a color (black or white), and the task was to check if there's a valid binary tree where each level has the same color.

My Approach:

1. I used graph traversal techniques to validate the structure.
2. For the follow-up, I considered level-order traversal to check color consistency.

Key Insights:

• Thorough understanding of graph properties and traversal algorithms is essential.
• Considering all possible edge cases and constraints is crucial for solving the problem.

Preparation Tips & Key Takeaways

What I Learned

• Communicating my thought process clearly to the interviewer is crucial.
• The interviewer provided helpful guidance, making the problem-solving process easier.

Recommended Preparation

Coding Practice

• Practice array manipulation and stream processing problems.
• Review graph traversal algorithms.

Data Structures

• Understand the properties of queues, graphs, and trees.

Common Pitfalls to Avoid

• Not considering all edge cases.
• Failing to communicate your approach clearly.