let path_of_string path_string =
   Str.(global_replace (regexp "[ >\\[\\]\\n]") "" path_string)

let path = "[0] -> 2 -> 1 -> 3 -> 7 -> 15 -> 12 -> 11 -> 9 -> 8 -> 10 -> 4 -> 14 -> 5 -> 6 -> [13]"
let () = print_endline path; print_endline @@ path_of_string path

(*prints
[0] -> 2 -> 1 -> 3 -> 7 -> 15 -> 12 -> 11 -> 9 -> 8 -> 10 -> 4 -> 14 -> 5 -> 6 -> [13]
[0] -> 2 -> 1 -> 3 -> 7 -> 15 -> 12 -> 11 -> 9 -> 8 -> 10 -> 4 -> 14 -> 5 -> 6 -> [13]
*)