Check out my new course Learn you some Lambda best practice for great good! and learn the best practices for performance, cost, security, resilience, observability and scalability.
ps. look out for all my other solutions for Advent of Code challenges here.
See details of the challenge here.
Today’s challenge is pretty straight forward, and a brute force approach would have suffice – try every t from 0 to inifinity and return the first t that satisfies this equation for all the discs:
(t + disc.Number – (disc.Positions – disc.Time0Position)) % disc.Positions = 0
That said, there’s a simple optimization we can apply by restricting ourselves to values of t that gets you through the first slot. Give my input for the challenge:
Disc #1 has 13 positions; at time=0, it is at position 11. Disc #2 has 5 positions; at time=0, it is at position 0. Disc #3 has 17 positions; at time=0, it is at position 11. Disc #4 has 3 positions; at time=0, it is at position 0. Disc #5 has 7 positions; at time=0, it is at position 2. Disc #6 has 19 positions; at time=0, it is at position 17.
The first t that will get us through disc #1 is t=1 where disc #1 reaches position 0 on t=2 (which is 1s away from t). From there, we only need to check every 13s, ie t=14, t=27, t=40, …
After getting the first capsule (it contained a star! what great fortune!), the
machine detects your success and begins to rearrange itself.
When it’s done, the discs are back in their original configuration as if it were
time=0 again, but a new disc with 11 positions and starting at position 0 has
appeared exactly one second below the previously-bottom disc.
With this new disc, and counting again starting from time=0 with the
configuration in your puzzle input, what is the first time you can press the
button to get another capsule?
- Day 15 challenge description
- Advent of Code 2015
- Solution for Day 14
- All my F# solutions for Advent of Code
- Github repo
I specialise in rapidly transitioning teams to serverless and building production-ready services on AWS.
Are you struggling with serverless or need guidance on best practices? Do you want someone to review your architecture and help you avoid costly mistakes down the line? Whatever the case, I’m here to help.
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Check out my new course, Learn you some Lambda best practice for great good! In this course, you will learn best practices for working with AWS Lambda in terms of performance, cost, security, scalability, resilience and observability. We will also cover latest features from re:Invent 2019 such as Provisioned Concurrency and Lambda Destinations. Enrol now and start learning!
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Here is a complete list of all my posts on serverless and AWS Lambda. In the meantime, here are a few of my most popular blog posts.
- Lambda optimization tip – enable HTTP keep-alive
- You are wrong about serverless and vendor lock-in
- You are thinking about serverless costs all wrong
- Just how expensive is the full AWS SDK?
- Many faced threats to Serverless security
- We can do better than percentile latencies
- Yubl’s road to Serverless
- AWS Lambda – should you have few monolithic functions or many single-purposed functions?
- AWS Lambda – compare coldstart time with different languages, memory and code sizes
- Guys, we’re doing pagination wrong
- Top 10 Serverless framework best practices