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Improve "winning" logic

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You don't need to check every possible win condition, just the one you
touched.
This commit is contained in:
Bert Peters
2021-12-14 19:51:57 +01:00
parent a35ae82548
commit a926243f0d
1 changed files with 28 additions and 12 deletions
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40
2021/src/day04.rs
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@@ -13,23 +13,35 @@ use nom::IResult;
struct BingoCard([(bool, u8); 25]); struct BingoCard([(bool, u8); 25]);
impl BingoCard { impl BingoCard {
pub fn cross(&mut self, num: u8) -> bool { pub fn cross(&mut self, num: u8) -> Option<usize> {
if let Some(card) = self.0.iter_mut().find(|&&mut (_, x)| x == num) { self.0
card.0 = true; .iter_mut()
true .enumerate()
} else { .find_map(|(pos, (ticked, x))| {
false if *x == num {
} *ticked = true;
Some(pos)
} else {
None
}
})
} }
pub fn has_won(&self) -> bool { pub fn has_won(&self, crossed: usize) -> bool {
// Check horizontal lines // Check horizontal lines
if self.0.chunks_exact(5).any(|s| s.iter().all(|&b| b.0)) { if self
.0
.chunks_exact(5)
.nth(crossed / 5)
.unwrap()
.iter()
.all(|&b| b.0)
{
return true; return true;
} }
// Check vertical lines // Check vertical lines
(0..5).any(|x| self.0.iter().skip(x).step_by(5).all(|b| b.0)) self.0.iter().skip(crossed % 5).step_by(5).all(|b| b.0)
// Diagonals do not count // Diagonals do not count
} }
@@ -81,7 +93,7 @@ pub fn part1(input: &mut dyn Read) -> String {
for number in numbers { for number in numbers {
for card in &mut bingo_cards { for card in &mut bingo_cards {
if card.cross(number) && card.has_won() { if matches!(card.cross(number), Some(pos) if card.has_won(pos)) {
return (number as u32 * card.remaining()).to_string(); return (number as u32 * card.remaining()).to_string();
} }
} }
@@ -98,7 +110,11 @@ pub fn part2(input: &mut dyn Read) -> String {
for num in numbers { for num in numbers {
for (won, card) in bingo_won.iter_mut().zip(bingo_cards.iter_mut()) { for (won, card) in bingo_won.iter_mut().zip(bingo_cards.iter_mut()) {
if !*won && card.cross(num) && card.has_won() { if *won {
continue;
}
if matches!(card.cross(num), Some(pos) if card.has_won(pos)) {
*won = true; *won = true;
num_won += 1; num_won += 1;