path: root/day6.ml

#use "topfind";;
#thread;;
#require "core";;
#require "stdio";;

open Core
open Stdio

let memory = In_channel.read_all "day6.txt"
             |> String.strip |> String.split ~on:'\t'
             |> Array.of_list |> Array.map ~f:int_of_string

let len = Array.length memory
let seen = Caml.Hashtbl.create 5000

let array_max xs =
  let f index (maxInd, maxVal) value =
    if value > maxVal then (index, value) else (maxInd, maxVal) in
  Array.foldi ~init:(0, 0) ~f:f xs

let rec redist xs n i =
  match n with
  | 0 -> ()
  | _ ->
     let pos = (i + 1) mod len in
     xs.(pos) <- xs.(pos) + 1;
     redist xs (n-1) pos

let rec cycle count banks =
  match Caml.Hashtbl.find_opt seen banks with
  | Some x ->
     Printf.printf "%d\n" count;
     Printf.printf "%d\n" (count - x)
  | None ->
     Caml.Hashtbl.add seen (Array.copy banks) count;
     let mi, mv = array_max banks in
     banks.(mi) <- 0;
     redist banks mv mi;
     cycle (count+1) banks

let () = cycle 0 memory