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|
import adglent.{First, Second}
import gleam/io
import gleam/dict.{type Dict}
import gleam/string
import gleam/list
import gleam/int
import gleam/order.{Eq}
import gleam/result
type Coord {
Coord(x: Int, y: Int)
}
type Symbol {
Number(Int)
Gear
OtherSymbol
Empty
}
type Board =
Dict(Coord, Symbol)
fn to_symbol(c: String) -> Symbol {
case int.parse(c), c {
Ok(n), _ -> Number(n)
Error(Nil), "." -> Empty
Error(Nil), "*" -> Gear
_, _ -> OtherSymbol
}
}
fn to_board(input: String) -> Board {
{
use y, r <- list.index_map(string.split(input, "\n"))
use x, c <- list.index_map(string.to_graphemes(r))
#(Coord(x, y), to_symbol(c))
}
|> list.flatten()
|> dict.from_list()
}
fn find_all_numbers(b: Board) {
b
|> dict.filter(fn(_, v) {
case v {
Number(_) -> True
_ -> False
}
})
|> dict.to_list()
|> list.sort(fn(a, b) {
let #(Coord(x_a, y_a), _) = a
let #(Coord(x_b, y_b), _) = b
case int.compare(y_a, y_b) {
Eq -> int.compare(x_a, x_b)
other -> other
}
})
}
fn group_parts(ns, acc) {
case ns, acc {
[], _ -> acc
[#(Coord(x, y) as c, Number(n)), ..t], [
#([Coord(x0, y0), ..] as cs, n0),
..acc_rest
] if y == y0 ->
case { x - 1 == x0 } {
True -> group_parts(t, [#([c, ..cs], n0 * 10 + n), ..acc_rest])
False -> group_parts(t, [#([c], n), ..acc])
}
[#(coord, Number(n)), ..t], _ -> group_parts(t, [#([coord], n), ..acc])
}
}
fn all_neighbors(c: Coord) -> List(Coord) {
let Coord(x, y) = c
use dx <- list.flat_map([-1, 0, 1])
use dy <- list.filter_map([-1, 0, 1])
case dx, dy {
0, 0 -> Error(Nil)
_, _ -> Ok(Coord(x + dx, y + dy))
}
}
fn check_part_neighbors(
part: #(List(Coord), Int),
board: Board,
) -> Result(Int, Nil) {
let #(coords, n) = part
let neighbors =
coords
|> list.flat_map(all_neighbors)
|> list.unique()
case
list.any(
neighbors,
fn(c) {
let content = dict.get(board, c)
content == Ok(OtherSymbol) || content == Ok(Gear)
},
)
{
True -> Ok(n)
False -> Error(Nil)
}
}
pub fn part1(input: String) {
let board = to_board(input)
board
|> find_all_numbers
|> group_parts([])
|> list.map(check_part_neighbors(_, board))
|> result.values
|> int.sum
}
fn find_gears(b: Board) {
dict.filter(b, fn(_, v) { v == Gear })
|> dict.keys
}
fn to_part_with_neighbors(part: #(List(Coord), Int)) {
let #(coords, n) = part
let neighbors =
coords
|> list.flat_map(all_neighbors)
|> list.unique
|> list.filter(fn(c) { !list.contains(coords, c) })
#(neighbors, n)
}
fn find_parts_near_gear(gear: Coord, parts: List(#(List(Coord), Int))) {
parts
|> list.filter_map(fn(part) {
let #(neighbors, n) = part
case list.contains(neighbors, gear) {
True -> Ok(n)
False -> Error(Nil)
}
})
}
fn keep_gears_near_two_parts(sets_of_parts: List(List(Int))) {
list.filter_map(
sets_of_parts,
fn(ps) {
case ps {
[p1, p2] -> Ok(p1 * p2)
_ -> Error(Nil)
}
},
)
}
pub fn part2(input: String) {
let board = to_board(input)
let parts =
board
|> find_all_numbers
|> group_parts([])
|> list.map(to_part_with_neighbors)
board
|> find_gears
|> list.map(find_parts_near_gear(_, parts))
|> keep_gears_near_two_parts
|> int.sum
}
pub fn main() {
let assert Ok(part) = adglent.get_part()
let assert Ok(input) = adglent.get_input("3")
case part {
First ->
part1(input)
|> adglent.inspect
|> io.println
Second ->
part2(input)
|> adglent.inspect
|> io.println
}
}
|
