part 9

9/main.ml

@@ -0,0 +1,107 @@
+open Printf;;
+open String;;
+
+let rec list_of_lines in_file =
+  try
+    let line = input_line in_file in
+    line :: list_of_lines(in_file)
+  with End_of_file ->
+    close_in in_file;
+    []
+
+let parse_filesystem_block index length =
+  if index mod 2 == 0 then
+    Array.init length (fun x -> index / 2)
+  else
+    Array.init length (fun x -> (-1))
+
+let digit_code_to_int c =
+  int_of_char c - int_of_char '0'
+
+let rec fix_file_layout_inner front_index back_index file_layout =
+  if front_index >= back_index then
+    ()
+  else if file_layout.(front_index) >= 0 then
+    fix_file_layout_inner (front_index + 1) back_index file_layout
+  else if file_layout.(back_index) < 0 then
+    fix_file_layout_inner front_index (back_index - 1) file_layout
+  else begin
+    file_layout.(front_index) <- file_layout.(back_index);
+    file_layout.(back_index) <- (-1);
+    fix_file_layout_inner (front_index + 1) (back_index - 1) file_layout
+  end
+
+let fix_file_layout file_layout =
+  let array_copy = Array.copy file_layout in
+  fix_file_layout_inner 0 (Array.length array_copy - 1) array_copy;
+  array_copy
+
+let rec get_repeated_count array value index step =
+  try 
+    if array.(index) != value then
+      0
+    else
+      1 + get_repeated_count array value (index + step) step
+  with Invalid_argument _ -> 0
+
+let rec try_move_file_no_fragment file_id file_index file_length file_layout front_index =
+  if front_index >= file_index then
+    ()
+  else if file_layout.(front_index) >= 0 then
+    try_move_file_no_fragment file_id file_index file_length file_layout (front_index + 1)
+  else
+    let free_space_length = get_repeated_count file_layout (-1) front_index 1 in
+    if free_space_length < file_length then
+      try_move_file_no_fragment file_id file_index file_length file_layout (front_index + free_space_length)
+    else begin
+      Seq.ints 0
+        |> Seq.take file_length
+        |> Seq.iter (
+          fun i ->
+            file_layout.(front_index + i) <- file_id;
+            file_layout.(file_index + i) <- (-1));
+    end
+
+let rec fix_file_layout_defragment_inner back_index file_layout =
+  if back_index < 0 then
+    ()
+  else if file_layout.(back_index) < 0 then
+    let free_space_length = get_repeated_count file_layout (-1) back_index (-1) in
+    fix_file_layout_defragment_inner (back_index - free_space_length) file_layout
+  else
+    let file_id = file_layout.(back_index) in
+    let file_length = get_repeated_count file_layout file_id back_index (-1) in
+    let new_back_index = back_index - file_length in
+    try_move_file_no_fragment file_id (new_back_index + 1) file_length file_layout 0;
+    fix_file_layout_defragment_inner new_back_index file_layout
+    
+
+let fix_file_layout_defragment file_layout = 
+  let array_copy = Array.copy file_layout in
+  fix_file_layout_defragment_inner (Array.length file_layout - 1) array_copy;
+  array_copy
+
+let get_checksum file_layout =
+  file_layout
+    |> Array.to_seq
+    |> Seq.mapi (fun i x -> i * x)
+    |> Seq.filter (fun x -> x >= 0)
+    |> Seq.fold_left Int.add 0
+
+let () =
+  let f = open_in "input.txt" in
+  let disk_map = f 
+    |> list_of_lines
+    |> List.hd
+    |> String.to_seq
+    |> Seq.map digit_code_to_int
+    |> List.of_seq in
+  let file_layout = disk_map
+    |> List.mapi (fun i x -> parse_filesystem_block i x)
+    |> Array.concat in
+  let fixed_layout = fix_file_layout file_layout in
+  let result = get_checksum fixed_layout in
+  printf "%d\n%!" result;
+  let fixed_layout_defragment = fix_file_layout_defragment file_layout in
+  let result2 = get_checksum fixed_layout_defragment in
+  printf "%d\n"result2