this post was submitted on 07 Dec 2024
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Advent Of Code

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Advent of Code is an annual Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like.

AoC 2024

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Day 7: Bridge Repair

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[โ€“] [email protected] 0 points 2 weeks ago* (last edited 2 weeks ago) (9 children)

Haskell

A surprisingly gentle one for the weekend! Avoiding string operations for concatenate got the runtime down to 1.291 secs on my machine.

import Control.Arrow
import Control.Monad
import Data.List
import Data.Maybe

readInput :: String -> [(Int, [Int])]
readInput = lines >>> map (break (== ':') >>> (read *** map read . words . tail))

equatable :: [Int -> Int -> Int] -> (Int, [Int]) -> Bool
equatable ops (x, ys) = elem x $ foldM apply 0 ys
  where
    apply a y = (\op -> a `op` y) <$> ops

concatenate :: Int -> Int -> Int
concatenate x y = x * mag y + y
  where
    mag z = fromJust $ find (> z) $ iterate (* 10) 10

main = do
  input <- readInput <$> readFile "input07"
  mapM_
    (print . sum . map fst . (`filter` input) . equatable)
    [ [(+), (*)],
      [(+), (*), concatenate]
    ]
[โ€“] [email protected] 0 points 2 weeks ago (4 children)

I wanted to this the way yo did, by repeatedly applying functions, but I didn't dare to because I like to mess up and spend some minutes debugging signatures, may I ask what your IDE setup is for the LSP-Hints with Haskell?
Setting up on my PC was a little bit of a pain because it needed matching ghc and ghcide versions, so I hadn't bothered doing it on my Laptop yet.

[โ€“] [email protected] 0 points 2 weeks ago (1 children)

I use neovim with haskell-tools.nvim plugin. For ghc, haskell-language-server and others I use nix which, among other benefits makes my development environment reproducible and all haskellPackages are built on the same version so there are no missmatches.

But, as much as I love nix, there are probably easier ways to setup your environment.

[โ€“] [email protected] 0 points 2 weeks ago

I just checked and I have haskell-tools.nvim on my PC but it somehow crashes the default config of the autocompletion for me, which I am too inexperienced to debug. I'll try it nonetheless, since I don't have autocompletion on the laptop anyways, thank you for the suggestion!

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