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Kinda did part 2

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This commit is contained in:
Dreaded_X 2023-12-21 16:21:24 +01:00
parent 6195d1579a
commit 6aaca41194
Signed by: Dreaded_X
GPG Key ID: 5A0CBFE3C3377FAA
1 changed files with 21 additions and 8 deletions
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29
2023/src/bin/day21.rs
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@ -27,7 +27,7 @@ mod tests {
#[test] #[test]
fn part2_test1() -> Result<()> { fn part2_test1() -> Result<()> {
Day::test(Day::part2, "test-1", 1) Day::test(Day::part2, "test-1", 154)
} }
// Benchmarks // Benchmarks
@ -113,8 +113,21 @@ impl aoc::Solver for Day {
fn part2(input: &str) -> Self::Output2 { fn part2(input: &str) -> Self::Output2 {
let height = input.lines().count(); let height = input.lines().count();
let width = input.lines().next().unwrap().chars().count(); let width = input.lines().next().unwrap().chars().count();
println!("{width}, {height}");
// Map is square: 131 x 131
// !!! Others have observed 26501365 = 202300 * 131 + 65 !!!
// Is there a pattern for i * 131 + 65?
// i = 0 => 3776
// i = 1 => 33652
// i = 2 => 93270
// Is there a function of i that can fit to this?
// Yes => Quadratic equation will fit this
// 3642 - 14737 x + 14871 x^2
// i = 202300 => 608603023105276
// Could not have done this without a hint from Reddit...
const N: usize = 2 * 131 + 65;
let mut queue = Vec::new(); let mut queue = VecDeque::new();
let map: HashMap<(isize, isize), char> = input let map: HashMap<(isize, isize), char> = input
.lines() .lines()
.enumerate() .enumerate()
@ -123,7 +136,7 @@ impl aoc::Solver for Day {
.enumerate() .enumerate()
.map(|(x, mut c)| { .map(|(x, mut c)| {
if c == 'S' { if c == 'S' {
queue.push(((x as isize, y as isize), 500)); queue.push_back(((x as isize, y as isize), 0));
c = '.'; c = '.';
} }
@ -136,7 +149,7 @@ impl aoc::Solver for Day {
let mut visited = HashSet::new(); let mut visited = HashSet::new();
let directions = [(-1, 0), (1, 0), (0, -1), (0, 1)]; let directions = [(-1, 0), (1, 0), (0, -1), (0, 1)];
// Depth first // Depth first
while let Some(step) = queue.pop() { while let Some(step) = queue.pop_front() {
// If we have already evaluated this state, do not add it to the queue // If we have already evaluated this state, do not add it to the queue
if visited.contains(&step) { if visited.contains(&step) {
continue; continue;
@ -146,7 +159,7 @@ impl aoc::Solver for Day {
visited.insert(step); visited.insert(step);
// Check if we have ran out of steps // Check if we have ran out of steps
if step.1 == 0 { if step.1 == N {
continue; continue;
} }
@ -154,7 +167,7 @@ impl aoc::Solver for Day {
for direction in directions { for direction in directions {
let next = ( let next = (
(step.0 .0 + direction.0, step.0 .1 + direction.1), (step.0 .0 + direction.0, step.0 .1 + direction.1),
step.1 - 1, step.1 + 1,
); );
let next_wrapped = ( let next_wrapped = (
@ -165,12 +178,12 @@ impl aoc::Solver for Day {
// If the tile is free add it to the queue // If the tile is free add it to the queue
if let Some(&tile) = map.get(&next_wrapped) { if let Some(&tile) = map.get(&next_wrapped) {
if tile == '.' { if tile == '.' {
queue.push(next); queue.push_back(next);
} }
} }
} }
} }
visited.iter().filter(|step| step.1 == 0).count() visited.iter().filter(|step| step.1 == N).count()
} }
} }