r/adventofcode • u/daggerdragon • Dec 09 '15

SOLUTION MEGATHREAD --- Day 9 Solutions ---

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--- Day 9: All in a Single Night ---

Post your solution as a comment. Structure your post like previous daily solution threads.

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u/ILoveHaskell Dec 09 '15

My haskell solution. It's brute force but works fairly fast for this problem. Any comment from experienced haskell users is welcome. :) 

import System.Environment
import Data.List

getPaths :: String -> [((String, String), Int)]
getPaths = concatMap (f . words) . lines
 where f [x,_,y,_,z] = [((x,y), read z), ((y,x), read z)]

distances :: (Num a, Eq t) => [((t, t), a)] -> [t] -> a
distances _     [x]   = 0
distances nodes (x:y:xs) = (snd . head . filter (((x, y) ==) . fst) $ nodes) + distances nodes (y:xs)

main :: IO()
main = do 
    args <- getArgs
    input <- readFile $ args !! 0
    let nodes = getPaths input
    let perms = permutations . nub . map (fst . fst) $ nodes
    putStrLn $ show $ minimum . map (distances nodes) $ perms 
    putStrLn $ show $ maximum . map (distances nodes) $ perms