3 files changed, 129 insertions(+), 0 deletions(-)

A 7/lex.mll
A 7/t1.ml
A 7/t2.ml

@@ 0,0 1,15 @@
+{
+type token =
+	| Cd of string
+  | File of int * string
+  | Cdup | Ls | Dir of string | Eof
+
+let i = int_of_string
+}
+
+rule token = parse
+	| "$ cd " ([^'\n']+ as d) '\n' { if d = ".." then Cdup else Cd d }
+  | "$ ls\n" { Ls }
+  | "dir " ([^'\n']+ as d) '\n' { Dir d }
+  | (['0'-'9']+ as sz) ' ' ([^'\n']+ as f) '\n' { File (i sz, f) }
+	| eof { Eof }

@@ 0,0 1,56 @@
+open Lex
+
+module StrMap = Map.Make(String)
+
+type thing =
+	| Dir of string
+	| File of int
+
+let joinpath l = List.fold_left (^) "" l
+
+let rec f lexbuf path (map: (thing list) StrMap.t) =
+	match Lex.token lexbuf with
+	| Eof -> map
+	| Cd dir -> f lexbuf (dir :: path) map
+	| Cdup -> f lexbuf (List.tl path) map
+	| Ls -> f lexbuf path map
+	| _ as tok ->
+		let map, update =
+			match tok with
+			| Dir d ->
+					let update e =
+						e |> Option.get |> List.cons (Dir d) |> Option.some
+					in
+					(StrMap.add (joinpath (d :: path)) [] map, update)
+			| File (sz, _) ->
+					let update e =
+						e |> Option.get |> List.cons (File sz) |> Option.some
+					in
+					(map, update)
+			| _ -> failwith "no way"
+		in
+		map |> StrMap.update (joinpath path) update |> f lexbuf path
+
+let mem = ref StrMap.empty
+
+let rec solve e map =
+	match StrMap.find_opt e !mem with
+	| Some v -> v
+	| None ->
+		let rec aux = function
+			| File sz :: l -> sz + aux l
+			| Dir d :: l -> solve (d ^ e) map + aux l
+			| [] -> 0
+		in
+		let res = StrMap.find e map |> aux in
+		mem := StrMap.add e res !mem;
+		res
+
+let sub_sum _ a = (+) (if a <= 100000 then a else 0)
+
+let () =
+	let map = StrMap.singleton "/" [] in
+	f (Lexing.from_channel stdin) [] map |>  solve "/" |> ignore;
+	StrMap.fold sub_sum !mem 0
+		|> Printf.printf "%d\n"
+

@@ 0,0 1,58 @@
+open Lex
+
+module StrMap = Map.Make(String)
+
+type thing =
+	| Dir of string
+	| File of int
+
+let joinpath l = List.fold_left (^) "" l
+
+let rec f lexbuf path (map: (thing list) StrMap.t) =
+	match Lex.token lexbuf with
+	| Eof -> map
+	| Cd dir -> f lexbuf (dir :: path) map
+	| Cdup -> f lexbuf (List.tl path) map
+	| Ls -> f lexbuf path map
+	| _ as tok ->
+		let map, update =
+			match tok with
+			| Dir d ->
+					let update e =
+						e |> Option.get |> List.cons (Dir d) |> Option.some
+					in
+					(StrMap.add (joinpath (d :: path)) [] map, update)
+			| File (sz, _) ->
+					let update e =
+						e |> Option.get |> List.cons (File sz) |> Option.some
+					in
+					(map, update)
+			| _ -> failwith "no way"
+		in
+		map |> StrMap.update (joinpath path) update |> f lexbuf path
+
+let mem = ref StrMap.empty
+
+let rec solve e map =
+	match StrMap.find_opt e !mem with
+	| Some v -> v
+	| None ->
+		let rec aux = function
+			| File sz :: l -> sz + aux l
+			| Dir d :: l -> solve (d ^ e) map + aux l
+			| [] -> 0
+		in
+		let res = StrMap.find e map |> aux in
+		mem := StrMap.add e res !mem;
+		res
+
+let find_optimal total _ cand curr =
+	if cand < curr && total - cand < 70_000_000 - 30_000_000 then cand
+	else curr
+
+let () =
+	let map = StrMap.singleton "/" [] in
+	let total = f (Lexing.from_channel stdin) [] map |>  solve "/" in
+	StrMap.fold (find_optimal total) !mem 70_000_000
+		|> Printf.printf "%d\n"
+