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2021: day04: use Vec::retain

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This commit is contained in:
Antoine Martin 2021-12-04 15:38:33 +01:00
parent 9209659a5a
commit 66fa27de0b
1 changed files with 19 additions and 20 deletions
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39
aoc2021/src/day04.rs
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@ -36,7 +36,8 @@ fn part1(input: &str) -> Result<u64> {
'draw_loop: for draw in draws {
for grid in &mut grids {
if grid.mark(draw) {
grid.mark(draw);
if grid.is_winning() {
wgrid = Some(grid.clone());
wdraw = Some(draw);
break 'draw_loop;
@ -74,21 +75,15 @@ fn part2(input: &str) -> Result<u64> {
.context("no draws available, didn't find last grid")?;
// TODO: replace with drain_filter when stabilized
let mut i = 0;
while i < grids.len() {
let grid = &mut grids[i];
if grid.mark(draw) {
grids.remove(i);
} else {
i += 1;
}
}
grids.iter_mut().for_each(|grid| grid.mark(draw));
grids.retain(|grid| !grid.is_winning());
}
let last_grid = &mut grids[0];
for draw in draws {
if last_grid.mark(draw) {
last_grid.mark(draw);
if last_grid.is_winning() {
return Ok(draw as u64 * last_grid.unmarked_numbers().map(|n| n as u64).sum::<u64>());
}
}
@ -102,23 +97,26 @@ struct Grid {
grid: [bool; GRID_SIZE],
rows: [u8; GRID_HEIGHT],
cols: [u8; GRID_WIDTH],
winning: bool,
}
impl Grid {
fn mark(&mut self, draw: u8) -> bool {
match self.number_to_pos.get(&draw) {
Some(&(x, y)) => {
*self.access_grid_mut(x, y) = true;
fn mark(&mut self, draw: u8) {
if let Some(&(x, y)) = self.number_to_pos.get(&draw) {
*self.access_grid_mut(x, y) = true;
self.rows[y] += 1;
self.cols[x] += 1;
self.rows[y] += 1;
self.cols[x] += 1;
self.rows[y] as usize == GRID_WIDTH || self.cols[x] as usize == GRID_HEIGHT
}
None => false,
self.winning =
self.rows[y] as usize == GRID_WIDTH || self.cols[x] as usize == GRID_HEIGHT;
}
}
fn is_winning(&self) -> bool {
self.winning
}
fn unmarked_numbers(&self) -> impl Iterator<Item = u8> + '_ {
self.number_to_pos
.iter()
@ -157,6 +155,7 @@ impl std::str::FromStr for Grid {
grid: [false; GRID_SIZE],
rows: [0; GRID_HEIGHT],
cols: [0; GRID_WIDTH],
winning: false,
})
}
}