Project Euler 26 by F# Ver.2

euler26_2.fs

/// https://gist.github.com/1430157#file_euler26.fs の改良（高速化）版
#light

let reccuringLength d =
    let rec loop i dict n =
        let r = n % d
        match Map.tryFind r dict with
        | Some j -> i - j
        | None -> loop (i+1) (Map.add r i dict) (r * 10)
    loop 0 Map.empty 1

let euler26 n =
    let rec loop d dMax lenMax =
        if lenMax >= d then
            dMax
        else
            let len = reccuringLength d
            if len > lenMax then
                loop (d-1) d len
            else
                loop (d-1) dMax lenMax
    loop n 0 0

printfn "%d" (euler26 999)