regnault.dev
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Day 4
+2
src/aoc.gleam
+2
src/aoc.gleam
···
3
3
import days/day1
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import days/day2
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import days/day3
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+
import days/day4
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import gleam/erlang
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import gleam/int
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import gleam/io
···
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1 -> day1.start()
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2 -> day2.start()
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3 -> day3.start()
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4 -> day4.start()
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_ -> io.println("Tried to run day " <> int.to_string(day))
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}
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birl.now()
+93
src/days/day4.gleam
+93
src/days/day4.gleam
···
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import gleam/dict
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import gleam/int
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import gleam/io
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import gleam/list
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import gleam/option
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import gleam/order
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import gleam/result
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import gleam/string
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import simplifile
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import utils/utils
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type Size {
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Size(height: Int, width: Int)
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}
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type Paper {
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Paper(x: Int, y: Int)
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}
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type Grid {
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Grid(dim: Size, cells: List(Paper))
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}
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pub fn start() -> Nil {
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let assert Ok(content) = simplifile.read("inputs/day4.txt")
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let data = parse(content)
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let _ = io.debug(part1(data))
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let _ = io.debug(part2(data))
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+
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Nil
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}
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+
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fn parse(data: String) {
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let splitted = string.split(data, "\n")
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let papers =
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splitted
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|> list.index_map(fn(line, idx_height) {
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string.to_graphemes(line)
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|> list.index_map(fn(y, idx_width) {
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case y {
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"@" -> option.Some(Paper(idx_width, idx_height))
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_ -> option.None
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}
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})
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})
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|> list.flatten
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|> list.filter(option.is_some)
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|> list.map(option.unwrap(_, Paper(-1, -1)))
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+
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let dim =
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Size(
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list.length(splitted),
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list.first(splitted) |> result.unwrap("") |> string.length,
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)
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Grid(dim, papers)
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}
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fn count_neighbours(cell: Paper, grid: Grid) {
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grid.cells
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|> list.filter(fn(paper) { !{ cell.x == paper.x && cell.y == paper.y } })
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|> list.filter(fn(paper) {
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case cell.x + 1 == paper.x || cell.x - 1 == paper.x || cell.x == paper.x {
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True ->
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cell.y + 1 == paper.y || cell.y - 1 == paper.y || cell.y == paper.y
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False -> False
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}
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})
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|> list.length
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}
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fn part1(data: Grid) {
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data.cells
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|> list.map(count_neighbours(_, data))
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|> list.filter(fn(x) { x < 4 })
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|> list.length
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}
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fn part2(data: Grid) {
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let to_remove =
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data.cells
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|> list.filter(fn(x) { count_neighbours(x, data) < 4 })
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case list.length(to_remove) {
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0 -> 0
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x -> {
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let new =
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data.cells
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|> list.filter(fn(x) { !list.contains(to_remove, x) })
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x + part2(Grid(data.dim, new))
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}
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}
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}