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use set for faster speed
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src/days/day4.gleam
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src/days/day4.gleam
···
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import gleam/list
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import gleam/option
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import gleam/result
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import gleam/set
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import gleam/string
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import simplifile
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···
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}
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type Grid {
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Grid(dim: Size, cells: List(Paper))
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Grid(dim: Size, cells: set.Set(Paper))
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}
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pub fn start() -> Nil {
···
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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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|> list.filter_map(option.to_result(_, Nil))
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|> list.fold(set.new(), fn(acc, x) { set.insert(acc, x) })
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let dim =
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Size(
···
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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) {
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!{ cell.x == paper.x && cell.y == paper.y }
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&& { cell.x + 1 == paper.x || cell.x - 1 == paper.x || cell.x == paper.x }
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&& { cell.y + 1 == paper.y || cell.y - 1 == paper.y || cell.y == paper.y }
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[#(-1, -1), #(-1, 0), #(-1, 1), #(0, -1), #(0, 1), #(1, -1), #(1, 0), #(1, 1)]
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|> list.filter(fn(offset) {
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set.contains(grid.cells, Paper(cell.x + offset.0, cell.y + offset.1))
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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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|> set.to_list
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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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let to_keep =
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data.cells
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|> list.filter(fn(x) { count_neighbours(x, data) < 4 })
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|> set.filter(fn(x) { count_neighbours(x, data) >= 4 })
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let to_remove = set.size(data.cells) - set.size(to_keep)
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case list.length(to_remove) {
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case 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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x + part2(Grid(data.dim, to_keep))
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}
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}
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}