From 552cdd2d958ab222614c68c7cb58af3116db4464 Mon Sep 17 00:00:00 2001
From: Hamcha <hamcha@crunchy.rocks>
Date: Sun, 15 Dec 2024 19:48:18 +0100
Subject: [PATCH] day 15 p1

---
 sample/day15-sample.txt  |  21 +++++
 sample/day15-sample2.txt |  10 +++
 src/day15_p1.gleam       | 163 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 194 insertions(+)
 create mode 100644 sample/day15-sample.txt
 create mode 100644 sample/day15-sample2.txt
 create mode 100644 src/day15_p1.gleam

diff --git a/sample/day15-sample.txt b/sample/day15-sample.txt
new file mode 100644
index 0000000..84cf1fb
--- /dev/null
+++ b/sample/day15-sample.txt
@@ -0,0 +1,21 @@
+##########
+#..O..O.O#
+#......O.#
+#.OO..O.O#
+#..O@..O.#
+#O#..O...#
+#O..O..O.#
+#.OO.O.OO#
+#....O...#
+##########
+
+<vv>^<v^>v>^vv^v>v<>v^v<v<^vv<<<^><<><>>v<vvv<>^v^>^<<<><<v<<<v^vv^v>^
+vvv<<^>^v^^><<>>><>^<<><^vv^^<>vvv<>><^^v>^>vv<>v<<<<v<^v>^<^^>>>^<v<v
+><>vv>v^v^<>><>>>><^^>vv>v<^^^>>v^v^<^^>v^^>v^<^v>v<>>v^v^<v>v^^<^^vv<
+<<v<^>>^^^^>>>v^<>vvv^><v<<<>^^^vv^<vvv>^>v<^^^^v<>^>vvvv><>>v^<<^^^^^
+^><^><>>><>^^<<^^v>>><^<v>^<vv>>v>>>^v><>^v><<<<v>>v<v<v>vvv>^<><<>^><
+^>><>^v<><^vvv<^^<><v<<<<<><^v<<<><<<^^<v<^^^><^>>^<v^><<<^>>^v<v^v<v^
+>^>>^v>vv>^<<^v<>><<><<v<<v><>v<^vv<<<>^^v^>^^>>><<^v>>v^v><^^>>^<>vv^
+<><^^>^^^<><vvvvv^v<v<<>^v<v>v<<^><<><<><<<^^<<<^<<>><<><^^^>^^<>^>v<>
+^^>vv<^v^v<vv>^<><v<^v>^^^>>>^^vvv^>vvv<>>>^<^>>>>>^<<^v>^vvv<>^<><<v>
+v^^>>><<^^<>>^v^<v^vv<>v^<<>^<^v^v><^<<<><<^<v><v<>vv>>v><v^<vv<>v^<<^
diff --git a/sample/day15-sample2.txt b/sample/day15-sample2.txt
new file mode 100644
index 0000000..8163605
--- /dev/null
+++ b/sample/day15-sample2.txt
@@ -0,0 +1,10 @@
+########
+#..O.O.#
+##@.O..#
+#...O..#
+#.#.O..#
+#...O..#
+#......#
+########
+
+<^^>>>vv<v>>v<<
diff --git a/src/day15_p1.gleam b/src/day15_p1.gleam
new file mode 100644
index 0000000..040cfb0
--- /dev/null
+++ b/src/day15_p1.gleam
@@ -0,0 +1,163 @@
+import gleam/dict.{type Dict}
+import gleam/io
+import gleam/iterator
+import gleam/list.{filter, map}
+import gleam/string
+import stdin.{stdin}
+
+pub fn main() {
+  stdin()
+  |> read_input
+  |> calculate
+  |> io.debug
+}
+
+fn calculate(input: #(Dict(#(Int, Int), Item), List(Movement))) -> Int {
+  let #(textmap, movements) = input
+  let #(robot, restmap) = extract_robot(textmap)
+
+  do_movements(restmap, robot, movements)
+  |> dict.filter(fn(_, v) { v == Box })
+  |> dict.fold(0, fn(acc, k, _) {
+    let #(x, y) = k
+    acc + x + y * 100
+  })
+}
+
+fn do_movements(
+  textmap: Dict(#(Int, Int), Item),
+  robot: #(Int, Int),
+  movements: List(Movement),
+) -> Dict(#(Int, Int), Item) {
+  case movements {
+    [] -> textmap
+    [next, ..rest] -> {
+      let #(newmap, newrobot) = move_robot(textmap, robot, next)
+      do_movements(newmap, newrobot, rest)
+    }
+  }
+}
+
+fn move_robot(
+  textmap: Dict(#(Int, Int), Item),
+  robot: #(Int, Int),
+  movement: Movement,
+) -> #(Dict(#(Int, Int), Item), #(Int, Int)) {
+  let next_pos = calculate_next_position(robot, movement)
+  case dict.get(textmap, next_pos) {
+    Ok(Wall) -> #(textmap, robot)
+    Ok(Box) ->
+      case try_move_box(textmap, next_pos, movement) {
+        Ok(new_map) -> #(new_map, next_pos)
+        _ -> #(textmap, robot)
+      }
+    _ -> #(textmap, next_pos)
+  }
+}
+
+fn try_move_box(
+  textmap: Dict(#(Int, Int), Item),
+  box_pos: #(Int, Int),
+  movement: Movement,
+) -> Result(Dict(#(Int, Int), Item), Nil) {
+  let next_pos = calculate_next_position(box_pos, movement)
+  case dict.get(textmap, next_pos) {
+    Ok(Wall) -> Error(Nil)
+    Ok(Box) ->
+      case try_move_box(textmap, next_pos, movement) {
+        Ok(new_map) ->
+          Ok(new_map |> dict.delete(box_pos) |> dict.insert(next_pos, Box))
+        _ -> Error(Nil)
+      }
+    _ -> Ok(textmap |> dict.delete(box_pos) |> dict.insert(next_pos, Box))
+  }
+}
+
+fn calculate_next_position(
+  current: #(Int, Int),
+  movement: Movement,
+) -> #(Int, Int) {
+  let #(x, y) = current
+  case movement {
+    Up -> #(x, y - 1)
+    Down -> #(x, y + 1)
+    Left -> #(x - 1, y)
+    Right -> #(x + 1, y)
+  }
+}
+
+fn extract_robot(
+  objects: Dict(#(Int, Int), Item),
+) -> #(#(Int, Int), Dict(#(Int, Int), Item)) {
+  let assert [robot] =
+    objects |> dict.filter(fn(_, v) { v == Robot }) |> dict.keys
+
+  #(robot, objects |> dict.delete(robot))
+}
+
+pub type Item {
+  Box
+  Wall
+  Robot
+}
+
+pub type Movement {
+  Up
+  Left
+  Right
+  Down
+}
+
+fn read_input(
+  it: iterator.Iterator(String),
+) -> #(Dict(#(Int, Int), Item), List(Movement)) {
+  let #(map_lines, movement_lines) =
+    it
+    |> iterator.to_list
+    |> map(string.trim)
+    |> filter(not(string.is_empty))
+    |> list.split_while(fn(s) { s |> string.starts_with("#") })
+
+  let map_objects =
+    map_lines
+    |> list.index_fold(dict.new(), parse_map_line)
+
+  let movements =
+    movement_lines
+    |> string.concat
+    |> string.to_graphemes
+    |> list.map(parse_movement)
+
+  #(map_objects, movements)
+}
+
+fn parse_map_line(
+  acc: Dict(#(Int, Int), Item),
+  line: String,
+  y: Int,
+) -> Dict(#(Int, Int), Item) {
+  line
+  |> string.to_graphemes
+  |> list.index_fold(acc, fn(a, char, x) {
+    case char {
+      "#" -> dict.insert(a, #(x, y), Wall)
+      "O" -> dict.insert(a, #(x, y), Box)
+      "@" -> dict.insert(a, #(x, y), Robot)
+      _ -> a
+    }
+  })
+}
+
+fn parse_movement(char: String) -> Movement {
+  case char {
+    "^" -> Up
+    "<" -> Left
+    ">" -> Right
+    "v" -> Down
+    _ -> panic as "invalid char"
+  }
+}
+
+fn not(a: fn(a) -> Bool) {
+  fn(param: a) -> Bool { !a(param) }
+}