gistfile1.fs

let rec move (x, y) r g n =
  if x < 0 || y < 0 || x > g || y > g then n 
  elif (x,y) = (g, g) then n + 1
  else match List.tryFind ((=) (x, y)) r with
        | Some _ -> n
        | None ->
                [(x + 1, y); (x, y + 1); (x - 1, y); (x, y - 1)] 
                |> List.map (fun xy -> move xy ((x, y)::r) g)
                |> List.fold (|>) n
 
[<EntryPoint>]
let main argv =
  let grids = int argv.[0]
  printfn "%A" (move (0,0) [] grids 0)
  0