Haskell

Oh, this one was easy (dynamic programming at last!). Still haven't figured out the right way to approach yesterday's part two, though.

import Data.List  
import Data.Map (Map)  
import Data.Map qualified as Map  

readInput =  
  Map.fromList  
    . map ((\(name : outs) -> (init name, outs)) . words)  
    . lines  

part1 input = go "you"  
  where  
    go "out" = 1  
    go name = maybe 0 (sum . map go) $ input Map.!? name  

part2 input = let (both, _, _, _) = pathsFrom "svr" in both  
  where  
    pathsFrom =  
      (Map.!)  
        . Map.insert "out" (0, 0, 0, 1)  
        . Map.fromList  
        . (zip <*> map findPaths)  
        $ Map.keys input ++ concat (Map.elems input)  
    findPaths n =  
      let (both, dac, fft, none) =  
            unzip4 $ maybe [] (map pathsFrom) (input Map.!? n)  
       in case n of  
            "dac" -> (sum both + sum fft, sum dac + sum none, 0, 0)  
            "fft" -> (sum both + sum dac, 0, sum fft + sum none, 0)  
            _ -> (sum both, sum dac, sum fft, sum none)  

main = do  
  input <- readInput <$> readFile "input11"  
  print $ part1 input  
  print $ part2 input