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import gleam/io
import gleam/int
import gleam/list
import gleam/bool
import gleam/string as str
import gleam/function as fun
import gleam/order.{Eq, Gt, Lt}
import ext/resultx as resx
import util/input_util
type GameState {
GameState(player1: List(Int), player2: List(Int))
}
fn parse_game_state(input: String) -> GameState {
let assert [player1, player2] =
input
|> str.trim()
|> str.split("\n\n")
|> list.map(with: fn(part) {
part
|> str.split("\n")
|> list.rest
|> resx.assert_unwrap
|> list.map(with: fun.compose(int.parse, resx.assert_unwrap))
})
GameState(player1, player2)
}
fn score(deck: List(Int)) -> Int {
deck
|> list.reverse
|> list.index_fold(
from: 0,
with: fn(sum, card, index) { sum + card * { index + 1 } },
)
}
fn play_combat_round(previous: GameState) -> Result(GameState, Int) {
let assert [top1, ..rest1] = previous.player1
let assert [top2, ..rest2] = previous.player2
let #(new1, new2) = case int.compare(top1, top2) {
Lt -> #(rest1, list.append(rest2, [top2, top1]))
Eq -> panic
Gt -> #(list.append(rest1, [top1, top2]), rest2)
}
use <- bool.guard(when: new1 == [], return: Error(score(new2)))
use <- bool.guard(when: new2 == [], return: Error(score(new1)))
Ok(GameState(new1, new2))
}
fn play_combat_game(initial: GameState) -> Int {
case play_combat_round(initial) {
Ok(next) -> play_combat_game(next)
Error(score) -> score
}
}
fn part1(input: String) -> Int {
input
|> parse_game_state
|> play_combat_game
|> int.absolute_value
}
pub fn main() -> Nil {
let test = input_util.read_text("test22")
let assert 306 = part1(test)
// let assert 291 = part2(test)
let input = input_util.read_text("day22")
io.debug(part1(input))
// io.debug(part2(input))
Nil
}
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