mystery-hunt-2023-reactivation/Reactivation/Seq.fs

namespace Reactivation

[<RequireQualifiedAccess>]
module Seq =

    let minMax (s : int seq) : struct (int * int) voption =
        use e = s.GetEnumerator ()

        if not (e.MoveNext ()) then
            ValueNone
        else

            let mutable min = e.Current
            let mutable max = e.Current

            while e.MoveNext () do
                if e.Current < min then
                    min <- e.Current

                if e.Current > max then
                    max <- e.Current

            ValueSome (struct (min, max))

    let rangeOrZero (s : int seq) : int =
        match minMax s with
        | ValueNone -> 0
        | ValueSome (min, max) -> max - min