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Implement 2022 day 24 part 2

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Bert Peters
2023-01-02 22:18:33 +01:00
parent 93c1d8f957
commit 4044af4d8d
1 changed files with 63 additions and 43 deletions
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106
2022/src/day24.rs
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@@ -55,6 +55,55 @@ impl Storm {
(self.height_period.get() - time % self.height_period + y) % self.height_period, (self.height_period.get() - time % self.height_period + y) % self.height_period,
)) ))
} }
fn dist(&self, from: (usize, usize), goal: (usize, usize), start: usize) -> Result<usize> {
let mut todo = VecDeque::new();
todo.push_back((start, from));
let mut visited = AHashSet::new();
while let Some((time, pos)) = todo.pop_front() {
let mut enqueue = |pos| {
let new_time = time + 1;
if self.can_stand(new_time, pos)
&& visited.insert((new_time % self.combined_period, pos))
{
todo.push_back((new_time, pos));
}
};
// Waiting is perhaps an option
enqueue(pos);
// If not in the starting position or the right edge
if pos.0 > 1 && pos.1 < self.height - 1 {
enqueue((pos.0 - 1, pos.1));
}
if pos.1 > 0 && pos.0 < self.width - 2 {
enqueue((pos.0 + 1, pos.1));
}
if pos.1 > 1 {
enqueue((pos.0, pos.1 - 1));
}
if pos.0 > 0 && pos.1 < self.height - 2 {
enqueue((pos.0, pos.1 + 1));
}
if pos.1 >= 1 && (pos.0, pos.1 - 1) == goal {
return Ok(time + 1);
}
if (pos.0, pos.1 + 1) == goal {
return Ok(time + 1);
}
}
anyhow::bail!("Did not find a route to {goal:?}")
}
} }
impl TryFrom<&'_ [u8]> for Storm { impl TryFrom<&'_ [u8]> for Storm {
@@ -111,51 +160,17 @@ pub fn part1(input: &[u8]) -> Result<String> {
let storm = Storm::try_from(input)?; let storm = Storm::try_from(input)?;
let goal = (storm.width - 2, storm.height - 1); let goal = (storm.width - 2, storm.height - 1);
let mut todo = VecDeque::new(); storm.dist((1, 0), goal, 0).map(|d| d.to_string())
todo.push_back((0, (1, 0)));
let mut visited = AHashSet::new();
while let Some((time, pos)) = todo.pop_front() {
let mut enqueue = |pos| {
let new_time = time + 1;
if storm.can_stand(new_time, pos)
&& visited.insert((new_time % storm.combined_period, pos))
{
todo.push_back((new_time, pos));
}
};
// Waiting is perhaps an option
enqueue(pos);
if pos.0 > 1 {
enqueue((pos.0 - 1, pos.1));
}
if pos.1 > 0 && pos.0 < storm.width - 2 {
enqueue((pos.0 + 1, pos.1));
}
if pos.1 > 1 {
enqueue((pos.0, pos.1 - 1));
}
if pos.0 > 0 && pos.1 < storm.height - 2 {
enqueue((pos.0, pos.1 + 1));
}
if (pos.0, pos.1 + 1) == goal {
return Ok((time + 1).to_string());
}
}
anyhow::bail!("Did not find a route to {goal:?}")
} }
pub fn part2(_input: &[u8]) -> Result<String> { pub fn part2(input: &[u8]) -> Result<String> {
anyhow::bail!("not implemented") let storm = Storm::try_from(input)?;
let goal = (storm.width - 2, storm.height - 1);
let there = storm.dist((1, 0), goal, 0)?;
let back_again = storm.dist(goal, (1, 0), there)?;
storm.dist((1, 0), goal, back_again).map(|s| s.to_string())
} }
#[cfg(test)] #[cfg(test)]
@@ -191,4 +206,9 @@ mod tests {
fn sample_part1() { fn sample_part1() {
assert_eq!(part1(SAMPLE).unwrap(), "18"); assert_eq!(part1(SAMPLE).unwrap(), "18");
} }
#[test]
fn sample_part2() {
assert_eq!(part2(SAMPLE).unwrap(), "54");
}
} }