aoc-2017-day3-part1-manhattan.fs

let part1 location = 
    let rowOffset ringId limit =
            match (location - limit) % (ringId * 2) with
            | 0                     -> ringId 
            | x when x - ringId < 0 -> (ringId - x) % ringId
            | x                     -> x % ringId

    location |> function
        | x when x <= 1 -> 0
        | x             -> 
            let (previousRing,limit) = rings |> Seq.takeWhile (snd >> ((>) x)) |> Seq.last
            match previousRing + 1 with
            | 1            -> 1 + (location % 2)
            | ringId       -> ringId + (rowOffset ringId limit)