2024-10 * ** Gleam

Author: Janiczek

src/aoc_2024/day_10.gleam

@@ -0,0 +1,84 @@
+import extra
+import gleam/int
+import gleam/list
+import gleam/set.{type Set}
+import grid.{type Grid, type XY}
+
+pub fn parse(input: String) -> Grid(Int) {
+ grid.from_string(input)
+ |> grid.map(fn(_, c) { extra.yolo_int(c) })
+}
+
+pub fn pt_1(input: Grid(Int)) {
+ let starting_positions: List(XY) = grid.find_all_exact(input, 0)
+ starting_positions
+ |> list.map(trailheads_count(input, _))
+ |> int.sum
+}
+
+pub fn pt_2(input: Grid(Int)) {
+ let starting_positions: List(XY) = grid.find_all_exact(input, 0)
+ starting_positions
+ |> list.map(trailheads_rating(input, _))
+ |> int.sum
+}
+
+type Trailhead {
+ Trailhead(xy: XY, height: Int)
+}
+
+fn trailheads_count(input: Grid(Int), start: XY) -> Int {
+ find_trailheads(
+ input,
+ todos: [Trailhead(xy: start, height: 0)],
+ count: 0,
+ seen: set.new(),
+ )
+ |> fn(x) { set.size(x.1) }
+}
+
+fn trailheads_rating(input: Grid(Int), start: XY) -> Int {
+ find_trailheads(
+ input,
+ todos: [Trailhead(xy: start, height: 0)],
+ count: 0,
+ seen: set.new(),
+ )
+ |> fn(x) { x.0 }
+}
+
+fn find_trailheads(
+ input: Grid(Int),
+ todos todos: List(Trailhead),
+ count count: Int,
+ seen seen: Set(XY),
+) -> #(Int, Set(XY)) {
+ case todos {
+ [] -> #(count, seen)
+ [todo_, ..rest] -> {
+ case todo_.height == 9 {
+ True ->
+ find_trailheads(
+ input,
+ todos: rest,
+ count: count + 1,
+ seen: set.insert(seen, todo_.xy),
+ )
+ False -> {
+ let added_todos =
+ grid.neighbours(input, todo_.xy, grid.orthogonal_dirs)
+ |> list.filter(fn(neighbour) { neighbour.1 == Ok(todo_.height + 1) })
+ |> list.map(fn(neighbour) {
+ Trailhead(xy: neighbour.0, height: todo_.height + 1)
+ })
+ find_trailheads(
+ input,
+ todos: list.append(rest, added_todos),
+ count: count,
+ seen: seen,
+ )
+ }
+ }
+ }
+ }
+}

src/aoc_2024/day_8.gleam

@@ -55,7 +55,6 @@ fn antinodes_xy_pt2(dims: Dims, pair: #(XY, XY)) -> List(XY) {
  )
 }
 
-/// Also return the start point
 fn cast_ray(dims: Dims, start: XY, d: XY, acc: List(XY)) -> List(XY) {
  let next = grid.xy_add(start, d)
  case grid.in_dims(dims, next) {

src/grid.gleam

@@ -415,3 +415,10 @@ pub fn show(
  })
  |> string.join("\n")
 }
+
+pub fn find_all_exact(grid: Grid(a), a: a) -> List(XY) {
+ grid.data
+ |> dict.to_list()
+ |> list.filter(fn(kv) { kv.1 == a })
+ |> list.map(fn(kv) { kv.0 })
+}