Note: deprecated.

See instead:

• https://github.com/sroccaserra/advent-of-code

Démarrer un nouveau projet

$ stack new aoc2018
$ stack setup
$ stack build

Usage

Those are equivalent:

$ stack runhaskell src/01.hs  # Uses corresponding src/XX.txt file by default
$ stack runhaskell src/01.hs src/01.txt  # Allows to choose the input file
$ stack runhaskell src/01.hs - < src/01.txt  # Allows to use stdin

Learnings

See also:

• https://github.com/sroccaserra/aoc2015#learnings
• https://github.com/sroccaserra/aoc2019#learnings
• https://github.com/sroccaserra/aoc2020#learnings
• https://github.com/sroccaserra/aoc2021#learnings
• https://github.com/sroccaserra/aoc2022#learnings

Algorithmes

• Summed-area table ~ https://en.wikipedia.org/wiki/Summed-area_table

  • A summed-area table is a data structure and algorithm for quickly and efficiently generating the sum of values in a rectangular subset of a grid.

• When confronted with huge numbers (billions!) of iterations in the secont part after a more reasonable first part, look for a stabilisation. For example, after 10 times the first part, does the result between two iterations become the same? Look for cycles also. If there is a constant delta or a cycle, this becomes an easy calculation.

Smalltalk

• The Collection #select:, #collect:, ... methods, and in general methods that accept a one-argument block also accept a method symbol for argument. Simply because the Symbol class has a #value: method. Nice.
• OrderedCollection makes for a good queue implementation. It has fast #removeFirst and #add: implementations. This is good for Breadth First Search like algorithms. Note: this is probably why there is no basic Queue class in the standard lib? There are a SharedQueue and WaitfreeQueue classes in my image though.
• There is a Heap class with #sortBlock: and #removeFirst methods. This is nice for Dijkstra-like algorithms.
• There are Point, G2DCoordinates and G3DCoordinates classes that can be used as Dictionary keys.
• This makes Smalltalk a pretty good language out of the box for the Advent of Code.
• When commiting changes to files in the Git repository (that are probably not Smalltalk code) outside the image, the view of the Git repository becomes dirty in the image. To fix that, open the Git repository in the image (right click and "Open repository"), this shows the commits in the repository, and by right-clicking them you can "adopt" them. This should fix the repository view in the image.

Haskell

• On peut construire un graph avec une liste d'arrêtes avec buildG ou graphFromEdges
• Un Vertex est un Int, une Edge est un (Int, Int), un Graph est un Array Int [Int]. On peut donc manipuler un graph avec les fonctions de Array.
• Vérifier un fichier sans le compiler : stack ghc -- -W -fno-code src/Common.hs
• Utiliser un label dans un pattern matching :
  • bb@(Coord minX minY, Coord maxX maxY) = boundingBox points
• Pattern simple vu plusieurs fois : utiliser une fonction go dans un where pour ammorcer les données initiales d'une fonction récursive (voir la partie 2 du jour 1)
• Combiner takeWhile et scanl pour appliquer une fonction à une liste d'entrée jusqu'à une condition sur le résultat (voir la deuxième partie du jour 1)
• Utiliser let pour affecter le résultat d'un calcul non IO dans une do notation (voir le main du jour 1)
• Générer une liste de liste de coordonnées (par exemple [[(Int, Int)]]) :
  • coordsGrid = map (\y -> (map (flip (,) y) [0..maxX])) [0..maxY]
  • coordsGrid = [[(x, y) | x <- [0..maxX]] | y <- [0..maxY]]
• Voir aussi range((0, 0), (maxX, maxY)) dans Data.Ix
• Appliquer une fonction sur toutes les coordonnées d'une liste de liste :
  • map f <$> coordsGrid
  • (appliquer map f au Functor List, soit map (map f) coordsGrid)