Project Euler 18

euler18.fs

let parseNumbersTriangle : string -> int list list =
    fun s ->
        s.Split([|'\n'|])
        |> Array.toList
        |> List.map (fun s ->
                     s.Trim().Split([|' '|])
                     |> Array.toList
                     |> List.map int)

let cutLast xs = xs |> Seq.take ((Seq.length xs) - 1) |> Seq.toList
let cutHead = List.tail
let greaters xs = List.map2 max (cutLast xs) (cutHead xs)

let solve : int list list -> int =
    fun nss ->
        nss
        |> List.rev
        |> List.reduce (fun xs ys -> 
                        xs |> greaters |> List.map2 (+) ys)
        |> List.head

let euler18 s = s |> parseNumbersTriangle |> solve

let data18Test =
    @"3
     7 4
    2 4 6
   8 5 9 3"

let data18 =
    @"75
    95 64
   17 47 82
    (中略)
63 66 04 68 89 53 67 30 73 16 69 87 40 31
04 62 98 27 23 09 70 98 73 93 38 53 60 04 23"

data18 |> euler18 |> printfn "%d"