parse day 15

src/day15.ml

@@ -0,0 +1,65 @@
+open Containers
+
+type sensor =
+  { pos : Vec2.t
+  ; beacon : Vec2.t
+  ; dist : int
+  }
+[@@deriving show { with_path = false }]
+
+let taxicab_dist a b =
+  let x, y = Vec2.(abs (a - b) |> to_tuple) in
+  x + y
+;;
+
+let parse_sensor line =
+  let open Utils.Parse in
+  let parse =
+    many1 (not_int *> int)
+    >>= function
+    | [ sx; sy; bx; by ] ->
+      let pos = Vec2.of_tuple (sx, sy) in
+      let beacon = Vec2.of_tuple (bx, by) in
+      return { pos; beacon; dist = taxicab_dist pos beacon }
+    | _ -> failwith "should be four ints"
+  in
+  Result.get_or_failwith @@ parse_string ~consume:All parse line
+;;
+
+let example_lines =
+  [ "Sensor at x=2, y=18: closest beacon is at x=-2, y=15"
+  ; "Sensor at x=9, y=16: closest beacon is at x=10, y=16"
+  ; "Sensor at x=13, y=2: closest beacon is at x=15, y=3"
+  ; "Sensor at x=12, y=14: closest beacon is at x=10, y=16"
+  ; "Sensor at x=10, y=20: closest beacon is at x=10, y=16"
+  ; "Sensor at x=14, y=17: closest beacon is at x=10, y=16"
+  ; "Sensor at x=8, y=7: closest beacon is at x=2, y=10"
+  ; "Sensor at x=2, y=0: closest beacon is at x=2, y=10"
+  ; "Sensor at x=0, y=11: closest beacon is at x=2, y=10"
+  ; "Sensor at x=20, y=14: closest beacon is at x=25, y=17"
+  ; "Sensor at x=17, y=20: closest beacon is at x=21, y=22"
+  ; "Sensor at x=16, y=7: closest beacon is at x=15, y=3"
+  ; "Sensor at x=14, y=3: closest beacon is at x=15, y=3"
+  ; "Sensor at x=20, y=1: closest beacon is at x=15, y=3"
+  ]
+;;
+
+let%expect_test "Day 15 example" =
+  example_lines |> List.map parse_sensor |> List.iter @@ Format.printf "%a@ " pp_sensor;
+  [%expect
+    {|
+    { pos = { Vec2.x = 2; y = 18 }; beacon = { Vec2.x = -2; y = 15 }; dist = 7 }
+    { pos = { Vec2.x = 9; y = 16 }; beacon = { Vec2.x = 10; y = 16 }; dist = 1 }
+    { pos = { Vec2.x = 13; y = 2 }; beacon = { Vec2.x = 15; y = 3 }; dist = 3 }
+    { pos = { Vec2.x = 12; y = 14 }; beacon = { Vec2.x = 10; y = 16 }; dist = 4 }
+    { pos = { Vec2.x = 10; y = 20 }; beacon = { Vec2.x = 10; y = 16 }; dist = 4 }
+    { pos = { Vec2.x = 14; y = 17 }; beacon = { Vec2.x = 10; y = 16 }; dist = 5 }
+    { pos = { Vec2.x = 8; y = 7 }; beacon = { Vec2.x = 2; y = 10 }; dist = 9 }
+    { pos = { Vec2.x = 2; y = 0 }; beacon = { Vec2.x = 2; y = 10 }; dist = 10 }
+    { pos = { Vec2.x = 0; y = 11 }; beacon = { Vec2.x = 2; y = 10 }; dist = 3 }
+    { pos = { Vec2.x = 20; y = 14 }; beacon = { Vec2.x = 25; y = 17 }; dist = 8 }
+    { pos = { Vec2.x = 17; y = 20 }; beacon = { Vec2.x = 21; y = 22 }; dist = 6 }
+    { pos = { Vec2.x = 16; y = 7 }; beacon = { Vec2.x = 15; y = 3 }; dist = 5 }
+    { pos = { Vec2.x = 14; y = 3 }; beacon = { Vec2.x = 15; y = 3 }; dist = 1 }
+    { pos = { Vec2.x = 20; y = 1 }; beacon = { Vec2.x = 15; y = 3 }; dist = 7 } |}]
+;;

src/utils.ml

@@ -13,11 +13,20 @@ let lines_of_input day =
 module Parse = struct
   include Angstrom
 
-  let int =
+  let sign = option 1 (char '-' >>= fun _ -> return (-1))
+
+  let digits =
     take_while1 (function
       | '0' .. '9' -> true
       | _ -> false)
     >>| int_of_string
-    <?> "int"
+  ;;
+
+  let int = map2 sign digits ~f:( * )
+
+  let not_int =
+    skip_while (function
+      | '0' .. '9' | '-' -> false
+      | _ -> true)
   ;;
 end

src/vec2.ml

@@ -17,3 +17,4 @@ let to_tuple { x; y } = x, y
 let ( + ) a b = { x = a.x + b.x; y = a.y + b.y }
 let ( - ) a b = { x = a.x - b.x; y = a.y - b.y }
 let ( = ) a b = a.x = b.x && a.y = b.y
+let abs a = Int.{ x = abs a.x; y = abs a.y }

src/vec2.mli

@@ -15,3 +15,4 @@ val to_tuple : t -> int * int
 val ( + ) : t -> t -> t
 val ( - ) : t -> t -> t
 val ( = ) : t -> t -> bool
+val abs : t -> t