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.
The input for today’s challenge looks like this:
rotate row y=0 by 10
rotate row y=0 by 10
rotate row y=0 by 5
rotate column x=43 by 1
rotate column x=40 by 2
rotate column x=38 by 1
So, our first task is to parse this input into something more workable (something like the Cmd union type we’ve declared below).
Notice that I used active patterns instead of plain functions:
- StartsWith returns the substring after the specified prefix
- SepBy returns the 2 numbers separated by either “x” or “by” (eg. “1×1”, “0 by 5”)
I find this style of parsing code easier to understand as it structurally matches the input line and mentally I don’t have to follow any branching logic.
Next, let’s model the screen and the different operations against it – rect, rotate row and rotate column.
Here I’ve gone with an imperative approach for efficiency sake, duplicating the 50×6 2D array repeatedly (at least once per command) just doesn’t sit well with me.
Anyhow, once we apply the commands parsed from the input file we need to count the no. of true elements in our 2D array to answer part 1.
You notice that the screen is only capable of displaying capital letters; in the
font it uses, each letter is 5 pixels wide and 6 tall.
After you swipe your card, what code is the screen trying to display?
To solve part 2, the easiest way I could think of was to print it out and see what letters are spelled out.
which in my case spelled out:
- Day 8 challenge description
- Advent of Code 2015
- Solution for Day 7
- 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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Are you working with Serverless and looking for expert training to level-up your skills? Or are you looking for a solid foundation to start from? Look no further, register for my Production-Ready Serverless workshop to learn how to build production-grade Serverless applications!
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