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|
import adglent.{First, Second}
import gleam/bool
import gleam/dict.{type Dict}
import gleam/int
import gleam/io
import gleam/list
import gleam/option.{None, Some}
import gleam/regex
import gleam/result
import gleam/set.{type Set}
import gleam/string
type Point {
Point(x: Int, y: Int, z: Int)
}
fn down_one(p: Point) -> Point {
Point(..p, z: p.z - 1)
}
type Block {
Block(index: Int, from: Point, to: Point)
}
fn compare_blocks(b1: Block, b2: Block) {
int.compare(b1.to.z, b2.to.z)
}
type Space =
Dict(Point, Block)
type AllBlocks =
Dict(Block, List(Point))
type BlockTree =
Dict(Int, Set(Int))
fn parse_block(index: Int, input: String) -> Block {
let assert Ok(re) = regex.from_string("(.*),(.*),(.*)~(.*),(.*),(.*)")
let assert [scan] = regex.scan(with: re, content: input)
let assert [x1, y1, z1, x2, y2, z2] =
scan.submatches
|> option.all
|> option.unwrap([])
|> list.map(int.parse)
|> result.values
Block(index: index, from: Point(x1, y1, z1), to: Point(x2, y2, z2))
}
fn cross_section_at_level(b: Block, z: Int) -> List(Point) {
use x <- list.flat_map(list.range(b.from.x, b.to.x))
use y <- list.map(list.range(b.from.y, b.to.y))
Point(x, y, z)
}
fn place_block(space: Space, b: Block, z: Int) -> Space {
let now_occupied = {
use x <- list.flat_map(list.range(b.from.x, b.to.x))
use y <- list.flat_map(list.range(b.from.y, b.to.y))
use z <- list.map(list.range(z, z + b.to.z - b.from.z))
#(Point(x, y, z), b)
}
dict.merge(space, dict.from_list(now_occupied))
}
fn find_lowest_level(space: Space, b: Block) -> Space {
do_find_lowest(space, b, b.from.z)
}
fn do_find_lowest(space: Space, b: Block, z: Int) -> Space {
let is_intersecting =
list.any(cross_section_at_level(b, z), dict.has_key(space, _))
case z, is_intersecting {
0, _ -> place_block(space, b, 1)
_, True -> place_block(space, b, z + 1)
_, False -> do_find_lowest(space, b, z - 1)
}
}
fn to_block_positions(space: Space) -> AllBlocks {
use acc, point, index <- dict.fold(space, dict.new())
use points <- dict.update(acc, index)
case points {
Some(ps) -> [point, ..ps]
None -> [point]
}
}
fn above_blocks(blocks: AllBlocks) -> BlockTree {
use acc, block, points <- dict.fold(blocks, dict.new())
use _ <- dict.update(acc, block.index)
{
use above_block, above_points <- dict.filter(blocks)
above_block.index != block.index
&& list.any(above_points, fn(p) { list.contains(points, down_one(p)) })
}
|> dict.keys
|> list.map(fn(b) { b.index })
|> set.from_list
}
fn below_blocks(blocktree: BlockTree) -> BlockTree {
use acc, block, _ <- dict.fold(blocktree, dict.new())
use _ <- dict.update(acc, block)
{
use _, aboves <- dict.filter(blocktree)
set.contains(aboves, block)
}
|> dict.keys
|> set.from_list
}
fn vulnerable_blocks(below_tree: BlockTree) -> List(Int) {
use block <- list.filter(dict.keys(below_tree))
use bs <- list.any(dict.values(below_tree))
!{ set.size(bs) == 0 } && { set.size(set.delete(bs, block)) == 0 }
}
pub fn part1(input: String) {
let settled_blocks =
input
|> string.split("\n")
|> list.index_map(parse_block)
|> list.sort(compare_blocks)
|> list.fold(dict.new(), find_lowest_level)
let block_positions = to_block_positions(settled_blocks)
let above_blocks = above_blocks(block_positions)
let below_blocks = below_blocks(above_blocks)
let vulnerable_blocks = vulnerable_blocks(below_blocks)
list.length(dict.keys(block_positions)) - list.length(vulnerable_blocks)
}
fn all_falling_blocks(n: Int, above: BlockTree, below: BlockTree) {
let starting_set = set.insert(set.new(), n)
do_falling_blocks(starting_set, starting_set, above, below)
}
fn do_falling_blocks(
fallen: Set(Int),
blocks: Set(Int),
above: BlockTree,
below: BlockTree,
) -> Int {
use <- bool.guard(set.size(blocks) == 0, set.size(fallen) - 1)
let blocks_above =
{
use block <- list.flat_map(set.to_list(blocks))
let assert Ok(supports) = dict.get(above, block)
use support <- list.filter(set.to_list(supports))
let assert Ok(supportings) = dict.get(below, support)
use supporting <- list.all(set.to_list(supportings))
set.contains(fallen, supporting)
}
|> set.from_list()
set.union(fallen, blocks_above)
|> do_falling_blocks(blocks_above, above, below)
}
pub fn part2(input: String) {
let settled_blocks =
input
|> string.split("\n")
|> list.index_map(parse_block)
|> list.sort(compare_blocks)
|> list.fold(dict.new(), find_lowest_level)
let block_positions = to_block_positions(settled_blocks)
let above_blocks = above_blocks(block_positions)
let below_blocks = below_blocks(above_blocks)
let vulnerable_blocks = vulnerable_blocks(below_blocks)
use acc, b <- list.fold(vulnerable_blocks, 0)
acc + all_falling_blocks(b, above_blocks, below_blocks)
}
pub fn main() {
let assert Ok(part) = adglent.get_part()
let assert Ok(input) = adglent.get_input("22")
case part {
First ->
part1(input)
|> adglent.inspect
|> io.println
Second ->
part2(input)
|> adglent.inspect
|> io.println
}
}
|
