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Implement 2023 day 16 part 2

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Bert Peters
2023-12-16 12:03:08 +01:00
parent c2389e93af
commit d78d74c92d
1 changed files with 53 additions and 16 deletions
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69
2023/src/day16.rs
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@@ -14,15 +14,12 @@ impl Direction {
} }
} }
pub fn part1(input: &[u8]) -> anyhow::Result<String> { fn compute_energized(
let map = Grid::new(input)?; map: &Grid<&[u8]>,
let mut state = Grid::zeroed(map.width(), map.height()); state: &mut Grid<Vec<u8>>,
state[0][0] = Direction::Right.bit(); todo: &mut Vec<(Direction, usize, usize)>,
) -> u32 {
let mut todo = Vec::new(); let mut energized = todo.len() as u32;
todo.push((Direction::Right, 0, 0));
let mut energized = 1;
while let Some((dir, x, y)) = todo.pop() { while let Some((dir, x, y)) = todo.pop() {
let mut enqueue = |dir: Direction, x: usize, y| { let mut enqueue = |dir: Direction, x: usize, y| {
@@ -90,11 +87,51 @@ pub fn part1(input: &[u8]) -> anyhow::Result<String> {
} }
} }
Ok(energized.to_string()) energized
} }
pub fn part2(_input: &[u8]) -> anyhow::Result<String> { pub fn part1(input: &[u8]) -> anyhow::Result<String> {
anyhow::bail!("Not implemented") let map = Grid::new(input)?;
let mut state = Grid::zeroed(map.width(), map.height());
state[0][0] = Direction::Right.bit();
let mut todo = Vec::new();
todo.push((Direction::Right, 0, 0));
Ok(compute_energized(&map, &mut state, &mut todo).to_string())
}
fn reset_state(state: &mut Grid<Vec<u8>>) {
for row in state.rows_mut() {
row.fill(0);
}
}
pub fn part2(input: &[u8]) -> anyhow::Result<String> {
let map = Grid::new(input)?;
let mut state = Grid::zeroed(map.width(), map.height());
let mut todo = Vec::new();
let mut helper = |dir: Direction, x, y| {
todo.push((dir, x, y));
reset_state(&mut state);
state[y][x] = dir.bit();
compute_energized(&map, &mut state, &mut todo)
};
let mut best = 0;
for x in 0..map.width() {
best = Ord::max(best, helper(Direction::Down, x, 0));
best = Ord::max(best, helper(Direction::Up, x, map.height() - 1));
}
for y in 0..map.height() {
best = Ord::max(best, helper(Direction::Down, 0, y));
best = Ord::max(best, helper(Direction::Up, map.width() - 1, y));
}
Ok(best.to_string())
} }
#[cfg(test)] #[cfg(test)]
@@ -108,8 +145,8 @@ mod tests {
assert_eq!("46", part1(SAMPLE).unwrap()); assert_eq!("46", part1(SAMPLE).unwrap());
} }
// #[test] #[test]
// fn sample_part2() { fn sample_part2() {
// assert_eq!("64", part2(SAMPLE).unwrap()); assert_eq!("51", part2(SAMPLE).unwrap());
// } }
} }