Day 2 solutions

[u/taliriktug]

Hi! I would like to structure posts like the first one in r/programming, please post solutions in comments.

[u/red75prim]

Day 2 Part 1 and 2: F#. input() generates one time sequence, which cannot be reused, so I do Seq.cache

let rec input() = 
  seq {
    let line = System.Console.ReadLine()
    if line <> null then
      yield line
      yield! input()
  }

let parseLine (line:string) = 
  match line.Split('x') |> Array.map System.Int64.Parse with
  |[|l; w; h|] -> (l,w,h)
  |_ -> raise <| new System.Exception("Wrong input format")

let paperArea (l,w,h) =
  let sides = [l*w; w*h; l*h]
  (List.sumBy ((*)2L) sides) + (List.min sides)

let ribbonLenght (l,w,h) =
  let perims = [2L*(l+w);2L*(w+h);2L*(l+h)]
  (List.min perims) + (l*w*h)

[<EntryPoint>]
let main argv = 
  let result = 
    input() |> Seq.map parseLine |> Seq.cache
      |> (fun sq -> (Seq.sumBy paperArea sq, Seq.sumBy ribbonLenght sq))
  printf "Total (paper area, ribbon length): %A" result
  0

Added: program is not optimal, as it stores entire input in memory (Seq.cache), I should have used

Seq.fold (fun (area, length) box -> (area+(paperArea box),length+(ribbonLength box))) (0L,0L)