--- /dev/null
+---
+title: "Advent of Code 2020"
+output: html_document
+css: modest.css
+---
+Code to solve the [Advent of Code](http://adventofcode.com/2020/) puzzles. This year, I'm using the puzzles to develop my skills in [Haskell](https://wiki.haskell.org/Haskell). I'm writing up a [commentary on these puzzles and my solutions](https://work.njae.me.uk/tag/advent-of-code/) on my blog.
+
+[Learn you a Haskell](http://learnyouahaskell.com/chapters), [Introduction to Haskell 98](https://www.haskell.org/tutorial/index.html), and [Hackage](https://hackage.haskell.org/) are good resources.
+
+The [Stack documentation](https://docs.haskellstack.org/en/stable/README/) and [How I Start: Haskell](http://howistart.org/posts/haskell/1/) are good sources of using the tools.
+
+
+# Toolchain
+
+Install Ghcup following [the instructions](https://www.haskell.org/ghcup/install/#installation), making sure to load the updated environment with
+
+```bash
+source /home/neil/.ghcup/env
+```
+
+Install [Haskell Language Server](https://haskell-language-server.readthedocs.io/en/latest/configuration.html) for Sublime Text
+
+
+## Creating the repository and project
+Create the repository as normal: create the project in Gitolite, clone it, and insert the `.gitignore` and `README.md` files.
+
+There's one package per day, with the code for each package in sub-directories of the root directory.
+
+Create the basic `cabal` project.
+
+```
+cabal init
+```
+
+Modify the `advent-of-code21.cabal` file as needed, such as updating the Cabal version and writing the `common` stanzas.
+
+## Creating subsequent days
+
+Each day lives in a separate directory, with its own `package.yaml` file and code in the `src` directory. (I based this configuration from [mstksg's setup](https://github.com/mstksg/advent-of-code-2018).)
+
+Compile with
+```
+cabal build
+```
+or
+```
+cabal build advent01
+```
+
+Run with
+```
+cabal run advent01
+```
+
+If you want to pass in additional RTS parameters, do it like this:
+```
+stack exec -- advent01 +RTS -K0 -RTS
+```
+
+Run interactively with
+```
+cabal repl advent01
+```
+or
+```
+stack ghci advent01:exe:advent01
+```
+if the first form is ambiguous.
+
+To profile, use
+```
+stack build --executable-profiling --library-profiling --ghc-options="-fprof-auto -rtsopts" advent01
+```
+then run with
+```
+stack exec --profile -- advent01 +RTS -p -hy
+```
+Generate the profile graph with
+```
+stack exec hp2ps advent01.hp
+```
+
+For Cabal, look at [profiling with Cabal sandboxes](https://nikita-volkov.github.io/profiling-cabal-projects/)
+
+
+# Packages
+
+Stack is using the [14.16-lts resolver](https://www.stackage.org/lts-16.25) for packages, so make sure you read the [correct documentation for the packages included in it](https://www.stackage.org/lts-16.25/docs).
+
+Packages I used a lot:
+
+* [Containers](https://hackage.haskell.org/package/containers) (and some [better documentation](https://haskell-containers.readthedocs.io/en/latest/intro.html)); [Unordered containers](https://hackage.haskell.org/package/unordered-containers) is a mostly-equivalent alternative.
+* [Attoparsec](https://hackage.haskell.org/package/attoparsec) (and [Megaparsec](https://hackage.haskell.org/package/megaparsec), and [ReadP](https://hackage.haskell.org/package/base-4.14.1.0/docs/Text-ParserCombinators-ReadP.html) once).
+
+There are somewhat decent [tutorials on Megaparsec](https://markkarpov.com/tutorial/megaparsec.html) and [Attoparsec](https://www.schoolofhaskell.com/school/starting-with-haskell/libraries-and-frameworks/text-manipulation/attoparsec).
+
+Packages I didn't use much, but need to remember:
+
+* [Arithmoi](https://hackage.haskell.org/package/arithmoi) for number theory
+* [Pointed List](https://hackage.haskell.org/package/pointedlist-0.6.1) for zipper lists (sometimes circular)
+* [Vector](https://hackage.haskell.org/package/vector) for array-like things
+* [Linear](https://hackage.haskell.org/package/linear) for coordinate-vector like things
+* [Grid](https://hackage.haskell.org/package/grid) for 2-d grids
+* [Graph-wrapper](https://hackage.haskell.org/package/graph-wrapper) for graphs
+* [Lens](https://hackage.haskell.org/package/lens) (and a [summary of operators](https://github.com/ekmett/lens/wiki/Operators)). I didn't use these much this year, but did a lot last year.
+* [RWS](https://hackage.haskell.org/package/mtl-2.2.2/docs/Control-Monad-RWS-Lazy.html) (Reader-Writer-State monad stack); again, used a lot last year but not this year
+* [Monad loops](https://hackage.haskell.org/package/monad-loops-0.4.3/docs/Control-Monad-Loops.html), and [a description](https://conscientiousprogrammer.com/blog/2015/12/11/24-days-of-hackage-2015-day-11-monad-loops-avoiding-writing-recursive-functions-by-refactoring/)
+* [Replace-Megaparsec](https://github.com/jamesdbrock/replace-megaparsec), for using Mpc for all sorts of things traditionally done with regex substitutions.
+
+# Readme
+
+Build this readme file wth
+```
+pandoc -s README.md > README.html
+```
+
+(Using the [Modest style](https://github.com/markdowncss/modest).)
--- /dev/null
+cabal-version: 3.6
+-- Initial package description 'advent-of-code21.cabal' generated by 'cabal
+-- init'. For further documentation, see
+-- http://haskell.org/cabal/users-guide/
+
+name: advent-of-code21
+version: 0.1.0.0
+synopsis: Advent of Code 21 solutions
+-- description:
+-- bug-reports:
+license: MIT
+-- license-file: LICENSE
+author: Neil Smith
+maintainer: neil.git@njae.me.uk
+-- copyright:
+-- category:
+build-type: Simple
+extra-source-files: CHANGELOG.md, README.md
+
+common common-extensions
+ default-extensions: AllowAmbiguousTypes
+ , ApplicativeDo
+ , BangPatterns
+ , BlockArguments
+ , DataKinds
+ , DeriveFoldable
+ , DeriveFunctor
+ , DeriveGeneric
+ , DeriveTraversable
+ , EmptyCase
+ , FlexibleContexts
+ , FlexibleInstances
+ , FunctionalDependencies
+ , GADTs
+ , GeneralizedNewtypeDeriving
+ , ImplicitParams
+ , KindSignatures
+ , LambdaCase
+ , MonadComprehensions
+ , MonoLocalBinds
+ , MultiParamTypeClasses
+ , MultiWayIf
+ , NamedFieldPuns
+ , NegativeLiterals
+ , NumDecimals
+ , OverloadedLists
+ , OverloadedStrings
+ , PartialTypeSignatures
+ , PatternGuards
+ , PatternSynonyms
+ , PolyKinds
+ , RankNTypes
+ , RecordWildCards
+ , ScopedTypeVariables
+ , TemplateHaskell
+ , TransformListComp
+ , TupleSections
+ , TypeApplications
+ , TypeFamilies
+ , TypeInType
+ , TypeOperators
+ , ViewPatterns
+
+common build-directives
+ build-depends: base ^>=4.14
+ default-language: Haskell2010
+ ghc-options: -O2
+ -Wall
+ -threaded
+ -rtsopts "-with-rtsopts=-N"
+
+executable advent-of-code21
+ main-is: Main.hs
+ -- other-modules:
+ -- other-extensions:
+ build-depends: base >=4.13 && < 4.15
+ -- hs-source-dirs:
+ default-language: Haskell2010
+
+executable advent01
+ import: common-extensions, build-directives
+ main-is: advent01/Main.hs
+ -- other-modules:
+ -- other-extensions:
+ -- build-depends: base >=4.13 && < 4.15
+ -- hs-source-dirs:
+ -- default-language: Haskell2010
\ No newline at end of file
--- /dev/null
+<!DOCTYPE html>
+<html lang="en-us">
+<head>
+<meta charset="utf-8"/>
+<title>Day 1 - Advent of Code 2021</title>
+<!--[if lt IE 9]><script src="/static/html5.js"></script><![endif]-->
+<link href='//fonts.googleapis.com/css?family=Source+Code+Pro:300&subset=latin,latin-ext' rel='stylesheet' type='text/css'/>
+<link rel="stylesheet" type="text/css" href="/static/style.css?26"/>
+<link rel="stylesheet alternate" type="text/css" href="/static/highcontrast.css?0" title="High Contrast"/>
+<link rel="shortcut icon" href="/favicon.png"/>
+</head><!--
+
+
+
+
+Oh, hello! Funny seeing you here.
+
+I appreciate your enthusiasm, but you aren't going to find much down here.
+There certainly aren't clues to any of the puzzles. The best surprises don't
+even appear in the source until you unlock them for real.
+
+Please be careful with automated requests; I'm not a massive company, and I can
+only take so much traffic. Please be considerate so that everyone gets to play.
+
+If you're curious about how Advent of Code works, it's running on some custom
+Perl code. Other than a few integrations (auth, analytics, social media), I
+built the whole thing myself, including the design, animations, prose, and all
+of the puzzles.
+
+The puzzles are most of the work; preparing a new calendar and a new set of
+puzzles each year takes all of my free time for 4-5 months. A lot of effort
+went into building this thing - I hope you're enjoying playing it as much as I
+enjoyed making it for you!
+
+If you'd like to hang out, I'm @ericwastl on Twitter.
+
+- Eric Wastl
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+-->
+<body>
+<header><div><h1 class="title-global"><a href="/">Advent of Code</a></h1><nav><ul><li><a href="/2021/about">[About]</a></li><li><a href="/2021/events">[Events]</a></li><li><a href="https://teespring.com/stores/advent-of-code" target="_blank">[Shop]</a></li><li><a href="/2021/settings">[Settings]</a></li><li><a href="/2021/auth/logout">[Log Out]</a></li></ul></nav><div class="user">Neil Smith <span class="star-count">2*</span></div></div><div><h1 class="title-event"> <span class="title-event-wrap">y(</span><a href="/2021">2021</a><span class="title-event-wrap">)</span></h1><nav><ul><li><a href="/2021">[Calendar]</a></li><li><a href="/2021/support">[AoC++]</a></li><li><a href="/2021/sponsors">[Sponsors]</a></li><li><a href="/2021/leaderboard">[Leaderboard]</a></li><li><a href="/2021/stats">[Stats]</a></li></ul></nav></div></header>
+
+<div id="sidebar">
+<div id="sponsor"><div class="quiet">Our <a href="/2021/sponsors">sponsors</a> help make Advent of Code possible:</div><div class="sponsor"><a href="https://www.capitalone.com/tech/" target="_blank" onclick="if(ga)ga('send','event','sponsor','sidebar',this.href);" rel="noopener">Capital One</a> - Leverage technology in new and powerful ways to pioneer change, all in the pursuit of changing banking for good. Join us!</div></div>
+</div><!--/sidebar-->
+
+<main>
+<script>window.addEventListener('click', function(e,s,r){if(e.target.nodeName==='CODE'&&e.detail===3){s=window.getSelection();s.removeAllRanges();r=document.createRange();r.selectNodeContents(e.target);s.addRange(r);}});</script>
+<article class="day-desc"><h2>--- Day 1: Sonar Sweep ---</h2><p>You're minding your own business on a ship at sea when the overboard alarm goes off! You rush to see if you can help. Apparently, one of the Elves tripped and accidentally sent the sleigh keys flying into the ocean!</p>
+<p>Before you know it, you're inside a submarine the Elves keep ready for situations like this. It's covered in Christmas lights (because of course it is), and it even has an experimental antenna that should be able to track the keys if you can boost its signal strength high enough; there's a little meter that indicates the antenna's signal strength by displaying 0-50 <em class="star">stars</em>.</p>
+<p>Your instincts tell you that in order to save Christmas, you'll need to get all <em class="star">fifty stars</em> by December 25th.</p>
+<p>Collect stars by solving puzzles. Two puzzles will be made available on each day in the Advent calendar; the second puzzle is unlocked when you complete the first. Each puzzle grants <em class="star">one star</em>. Good luck!</p>
+<p>As the submarine drops below the surface of the ocean, it automatically performs a sonar sweep of the nearby sea floor. On a small screen, the sonar sweep report (your puzzle input) appears: each line is a measurement of the sea floor depth as the sweep looks further and further away from the submarine.</p>
+<p>For example, suppose you had the following report:</p>
+<pre><code>199
+200
+208
+210
+200
+207
+240
+269
+260
+263
+</code></pre>
+<p>This report indicates that, scanning outward from the submarine, the sonar sweep found depths of <code>199</code>, <code>200</code>, <code>208</code>, <code>210</code>, and so on.</p>
+<p>The first order of business is to figure out how quickly the depth increases, just so you know what you're dealing with - you never know if the keys will get <span title="Does this premise seem fishy to you?">carried into deeper water</span> by an ocean current or a fish or something.</p>
+<p>To do this, count <em>the number of times a depth measurement increases</em> from the previous measurement. (There is no measurement before the first measurement.) In the example above, the changes are as follows:</p>
+<pre><code>199 (N/A - no previous measurement)
+200 (<em>increased</em>)
+208 (<em>increased</em>)
+210 (<em>increased</em>)
+200 (decreased)
+207 (<em>increased</em>)
+240 (<em>increased</em>)
+269 (<em>increased</em>)
+260 (decreased)
+263 (<em>increased</em>)
+</code></pre>
+<p>In this example, there are <em><code>7</code></em> measurements that are larger than the previous measurement.</p>
+<p><em>How many measurements are larger than the previous measurement?</em></p>
+</article>
+<p>Your puzzle answer was <code>1521</code>.</p><article class="day-desc"><h2 id="part2">--- Part Two ---</h2><p>Considering every single measurement isn't as useful as you expected: there's just too much noise in the data.</p>
+<p>Instead, consider sums of a <em>three-measurement sliding window</em>. Again considering the above example:</p>
+<pre><code>199 A
+200 A B
+208 A B C
+210 B C D
+200 E C D
+207 E F D
+240 E F G
+269 F G H
+260 G H
+263 H
+</code></pre>
+<p>Start by comparing the first and second three-measurement windows. The measurements in the first window are marked <code>A</code> (<code>199</code>, <code>200</code>, <code>208</code>); their sum is <code>199 + 200 + 208 = 607</code>. The second window is marked <code>B</code> (<code>200</code>, <code>208</code>, <code>210</code>); its sum is <code>618</code>. The sum of measurements in the second window is larger than the sum of the first, so this first comparison <em>increased</em>.</p>
+<p>Your goal now is to count <em>the number of times the sum of measurements in this sliding window increases</em> from the previous sum. So, compare <code>A</code> with <code>B</code>, then compare <code>B</code> with <code>C</code>, then <code>C</code> with <code>D</code>, and so on. Stop when there aren't enough measurements left to create a new three-measurement sum.</p>
+<p>In the above example, the sum of each three-measurement window is as follows:</p>
+<pre><code>A: 607 (N/A - no previous sum)
+B: 618 (<em>increased</em>)
+C: 618 (no change)
+D: 617 (decreased)
+E: 647 (<em>increased</em>)
+F: 716 (<em>increased</em>)
+G: 769 (<em>increased</em>)
+H: 792 (<em>increased</em>)
+</code></pre>
+<p>In this example, there are <em><code>5</code></em> sums that are larger than the previous sum.</p>
+<p>Consider sums of a three-measurement sliding window. <em>How many sums are larger than the previous sum?</em></p>
+</article>
+<p>Your puzzle answer was <code>1543</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
+<p>At this point, you should <a href="/2021">return to your Advent calendar</a> and try another puzzle.</p>
+<p>If you still want to see it, you can <a href="1/input" target="_blank">get your puzzle input</a>.</p>
+<p>You can also <span class="share">[Share<span class="share-content">on
+ <a href="https://twitter.com/intent/tweet?text=I%27ve+completed+%22Sonar+Sweep%22+%2D+Day+1+%2D+Advent+of+Code+2021&url=https%3A%2F%2Fadventofcode%2Ecom%2F2021%2Fday%2F1&related=ericwastl&hashtags=AdventOfCode" target="_blank">Twitter</a>
+ <a href="javascript:void(0);" onclick="var mastodon_instance=prompt('Mastodon Instance / Server Name?'); if(typeof mastodon_instance==='string' && mastodon_instance.length){this.href='https://'+mastodon_instance+'/share?text=I%27ve+completed+%22Sonar+Sweep%22+%2D+Day+1+%2D+Advent+of+Code+2021+%23AdventOfCode+https%3A%2F%2Fadventofcode%2Ecom%2F2021%2Fday%2F1'}else{return false;}" target="_blank">Mastodon</a
+></span>]</span> this puzzle.</p>
+</main>
+
+<!-- ga -->
+<script>
+(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
+(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
+m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
+})(window,document,'script','//www.google-analytics.com/analytics.js','ga');
+ga('create', 'UA-69522494-1', 'auto');
+ga('set', 'anonymizeIp', true);
+ga('send', 'pageview');
+</script>
+<!-- /ga -->
+</body>
+</html>
\ No newline at end of file
projects / advent-of-code-21.git / commitdiff