open System

open System.Diagnostics

let a = [|"helrlo1234567890"; "1234567890hello";"llohe1234567890";"1234567890nonono"|]

let b = "1234567890olelh"

​

let singlePassAnagram (x:string) =

    x

    |> Seq.groupBy (fun c -> c)

    |> Seq.sortBy (fun (c,g) -> c)

    |> Seq.map (fun  (c,g) -> 

        (c, g |> Seq.length ))

    |> Seq.toArray 

let areAnagramsFast 

        (x:string)

        (y:string) =

    if x.Length <> y.Length

    then false else

    (singlePassAnagram x) = 

        (singlePassAnagram y)

​

let rec areAnagramRec

        (x:string)

        (y:string) =  

    if x.Length <> y.Length 

    then false else

    if x.Length = 0

    then true else

    let repl = x.[0].ToString()

    areAnagramRec

        (x.Replace(repl,""))

        (y.Replace(repl,""))

​

let anagram (x:string) =

    x.ToLower()

    |> Seq.sort 

    |> Seq.toArray

let anagrBySort x y =

        anagram x = anagram y

let areAnagram arr y f =

    arr 

    |> Seq.filter (fun x ->

        f x y)

    |> Seq.toArray 

let sw=Stopwatch()

sw.Start()

printfn "anag by sort of %s: %A" b

    <| areAnagram a b anagrBySort

sw.Stop ()

let elapsed = sw.ElapsedMilliseconds

sw.Reset()

printfn "sort ms: %i" elapsed

sw.Start()

printfn "and by recursion %A"

    <| areAnagram a b areAnagramRec

sw.Stop ()

printfn "Rec ms: %i" sw.ElapsedMilliseconds

sw.Reset()

sw.Start ()

printfn "and fast %A"

    <| areAnagram a b areAnagramsFast

sw.Stop()

printfn "Fast ms %i" sw.ElapsedMilliseconds