MatchingSubgroup.fs

let (|Empty|_|) = function
    | xs when Set.isEmpty xs -> Some ()
    | _ -> None

[
    "rule1", ["192"; "193"]
    "rule2", ["193"; "194"]
    "rule3", ["194"; "195"]
]
|> Seq.fold (fun data (rule, dst) ->
    let dst = set dst
    data
    |> Map.toSeq
    |> Seq.map (fun (dsts, rules) ->
        let common = Set.intersect dsts dst
        common, rules
    )
    |> Seq.sortBy (fun (common, _) -> -common.Count)
    |> Seq.fold (fun (data, dst) (common, rules) ->
        match dst with
        | Empty -> data, dst
        | _ -> Map.add common (rule :: rules) data, dst - common
    ) (data, dst)
    |>  function
        | newData, Empty -> newData
        | newData, rest -> newData.Add(rest, [rule])
) Map.empty