Software Engineer · Phone Screen · Coding

Amazon — Software Engineer ✅ Passed

Level: Junior-Level

Round: Phone Screen · Type: Coding · Difficulty: 7/10 · Duration: 60 min · Interviewer: Neutral

Topics: Graph Theory, Topological Sort

Location: Seattle, WA, US

Interview date: 2026-01-20

Summary

Round 1: Phone Screen

Question: Determine which services will be affected when certain services are shut down, given dependencies between Amazon services. The problem is to be solved using topological sort.

Details

The interviewer presented the problem verbally. The problem involves determining the impact of shutting down certain services within Amazon, given the dependencies between services.

First, I clarified the question by asking about the input format. The input is a hashmap where the key is the service name, and the value is a list of services that depend on it. I also asked if there could be invalid inputs like cycles, but was told the input is guaranteed to be valid.

My approach:

1. Calculate the in-degree of each service.
2. Add services with an in-degree of 0 to a queue.
3. Initialize a set of affected services, initially containing the shut-down services.
4. While the queue is not empty, pop the first service from the queue.
5. Iterate through the dependent services. If the current service is in the affected services set, add the dependent service to the set and update its in-degree. If the in-degree becomes 0, add it to the queue.
6. When the queue is empty, return the set of affected services.

I explained my approach before coding, since the code cannot be run directly during the interview.