day 13

13/main.ml

@@ -0,0 +1,55 @@
+open Printf;;
+open Buffer;;
+open Str;;
+
+let read_whole_file f =
+  let s = really_input_string f (in_channel_length f) in
+  close_in f;
+  s
+
+let rec find_all_numbers pos str  =
+  try
+    let re = Str.regexp "[0-9]+" in
+    let new_pos = Str.search_forward re str pos in
+    let n_str = Str.matched_group 0 str in
+    let n = int_of_string n_str in
+    n :: find_all_numbers (new_pos + String.length n_str) str 
+  with Not_found -> []
+
+let rec to_sextuples lst =
+  match lst with
+  | n1 :: n2 :: n3 :: n4 :: n5 :: n6 :: tail ->
+    (n1, n2, n3, n4, n5, n6) :: to_sextuples tail
+  | _ -> []
+
+let rec get_cost (ax, ay, bx, by, cx, cy) =
+  let det = ax * by - ay * bx in
+  if det = 0 then
+    raise (Invalid_argument "Linearly dependent")
+  else
+    let det_a = cx * by - cy * bx in
+    let det_b = ax * cy - ay * cx in
+    if det_a mod det = 0 && det_b mod det = 0 then
+      (det_a / det) * 3 + (det_b / det)
+    else
+      0
+
+let correct_position (ax, ay, bx, by, cx, cy) =
+  (ax, ay, bx, by, cx + 10000000000000, cy + 10000000000000)
+
+let () =
+  let f = open_in "input.txt" in
+  let numbers = f
+    |> read_whole_file
+    |> find_all_numbers 0
+    |> to_sextuples in
+  let result = numbers
+    |> List.map get_cost 
+    |> List.fold_left Int.add 0 in
+  let result2 = numbers
+    |> List.map correct_position
+    |> List.map get_cost
+    |> List.fold_left Int.add 0 in
+  printf "%d\n%d\n" result result2
+  
+