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Day 21 refactoring

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kageru 2021-12-22 00:29:21 +01:00
parent c47f381a3b
commit b262f734b5
Signed by: kageru
GPG Key ID: 8282A2BEA4ADA3D2
1 changed files with 26 additions and 31 deletions
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57
2021/src/bin/day21.rs
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@ -10,15 +10,12 @@ fn part1((p1, p2): Parsed) -> usize {
.cycle()
.skip(1)
.step_by(3)
.zip(1..)
.scan([(p2, 0), (p1, 0)], |mut scores, (die, round)| {
let mut points = scores[round & 1].0 + die * 3;
points -= (points - 1) / 10 * 10;
scores[round & 1].0 = points;
scores[round & 1].1 += points;
Some((round, (scores[0].1, scores[1].1)))
.scan(GameState { odd_round: false, scores: [(p1, 0), (p2, 0)] }, |mut game, die| {
advance_game(&mut game, die * 3);
Some((game.scores[0].1, game.scores[1].1))
})
.find_map(|(r, (s1, s2))| (s1 >= 1000 || s2 >= 1000).then(|| r * 3 * (s1.min(s2) as usize)))
.zip(1..)
.find_map(|((s1, s2), r)| (s1 >= 1000 || s2 >= 1000).then(|| r * 3 * (s1.min(s2) as usize)))
.unwrap()
}
@ -37,33 +34,31 @@ fn part2((p1, p2): Parsed) -> usize {
let start = GameState { odd_round: false, scores: [(p1, 0), (p2, 0)] };
let mut games = FnvHashMap::default();
games.insert(start, 1);
let mut p1_wins = 0;
let mut p2_wins = 0;
let mut wins = [0, 0];
while !games.is_empty() {
games = games
.iter()
.flat_map(|(start, count)| POSSIBLE_ROLLS.iter().map(move |(die, count2)| (start, count * count2, die)))
.map(|(start, count, die)| {
let mut scores = start.scores;
let mut points = scores[start.odd_round as usize].0 + die;
points -= (points - 1) / 10 * 10;
scores[start.odd_round as usize].0 = points;
scores[start.odd_round as usize].1 += points as usize;
(GameState { odd_round: !start.odd_round, scores }, count)
})
.fold(FnvHashMap::default(), |mut acc, (state, count)| {
// Remove done games and queue the rest for another round
if state.scores[0].1 >= 21 {
p1_wins += count;
} else if state.scores[1].1 >= 21 {
p2_wins += count;
for k in games.clone().keys() {
let (start, count) = games.remove_entry(k).unwrap();
for &(die, count2) in &POSSIBLE_ROLLS {
let mut new_state = start;
advance_game(&mut new_state, die);
if new_state.scores[start.odd_round as usize].1 >= 21 {
wins[new_state.odd_round as usize] += count * count2;
} else {
*acc.entry(state).or_insert(0) += count;
*games.entry(new_state).or_insert(0) += count * count2;
}
acc
})
}
}
}
p1_wins.max(p2_wins)
wins[0].max(wins[1])
}
fn advance_game(game: &mut GameState, die: u16) {
let index = game.odd_round as usize;
let mut points = game.scores[index].0 + die;
points -= (points - 1) / 10 * 10;
game.scores[index].0 = points;
game.scores[index].1 += points as usize;
game.odd_round = !game.odd_round;
}
fn main() {