109 lines
2.3 KiB
Gleam
109 lines
2.3 KiB
Gleam
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import gleam/dict.{type Dict}
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import gleam/io
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import gleam/iterator.{Done, Next}
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import gleam/list.{filter, fold, map}
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import gleam/pair
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import gleam/result
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import gleam/string
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import stdin.{stdin}
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pub fn main() {
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stdin()
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|> read_input
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|> calculate_resonance
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|> io.debug
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}
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fn calculate_resonance(chart: Map) -> Int {
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let Map(w, h, antennas) = chart
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antennas
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|> dict.fold([], fn(acc, _, coords) {
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let antinodes =
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coords
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|> ordered_combinations
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|> map(fn(coord) {
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let #(dx, dy) = resolve_antinode_frequency(coord)
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// Spawn antinodes until out ot bounds
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coord
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|> pair.first
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|> iterator.unfold(fn(pos) {
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let #(x, y) = pos
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let newpos = #(x + dx, y + dy)
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case newpos {
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#(tx, ty) if tx < 0 || tx >= w || ty < 0 || ty >= h -> Done
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_ -> Next(newpos, newpos)
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}
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})
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|> iterator.to_list
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})
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|> list.flatten
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[coords, antinodes, acc] |> list.flatten
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})
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|> list.unique
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|> list.length
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}
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fn resolve_antinode_frequency(
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coords: #(#(Int, Int), #(Int, Int)),
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) -> #(Int, Int) {
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let #(#(ax, ay), #(bx, by)) = coords
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#(ax - bx, ay - by)
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}
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fn ordered_combinations(items: List(a)) -> List(#(a, a)) {
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items
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|> list.combination_pairs
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|> map(fn(x) { [x, pair.swap(x)] })
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|> list.flatten
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}
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pub type Map {
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Map(width: Int, height: Int, antennas: Dict(String, List(#(Int, Int))))
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}
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fn read_input(it: iterator.Iterator(String)) -> Map {
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let maptxt =
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it
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|> iterator.to_list
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|> map(string.trim)
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|> filter(not(string.is_empty))
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let assert Ok(width) = list.first(maptxt) |> result.map(string.length)
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let height = list.length(maptxt)
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let antennas =
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maptxt
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|> list.index_fold([], find_antennas)
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|> fold(dict.new(), fn(acc, v) {
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let #(group, coord) = v
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let current =
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acc
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|> dict.get(group)
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|> result.unwrap([])
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dict.insert(acc, group, [coord, ..current])
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})
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Map(width, height, antennas)
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}
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fn find_antennas(
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acc: List(#(String, #(Int, Int))),
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line: String,
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y: Int,
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) -> List(#(String, #(Int, Int))) {
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line
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|> string.to_graphemes
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|> list.index_fold(acc, fn(cur, chr, x) {
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case chr {
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"." -> cur
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c -> [#(c, #(x, y)), ..cur]
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}
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})
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}
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fn not(a: fn(a) -> Bool) {
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fn(param: a) -> Bool { !a(param) }
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}
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