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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,7 @@ | ||
| [package] | ||
| name = "AoC2023_21" | ||
| version = "0.1.0" | ||
| edition = "2021" | ||
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| [dependencies] | ||
| aoc = { path = "../aoc" } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,106 @@ | ||
| #![allow(non_snake_case)] | ||
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| use std::collections::HashSet; | ||
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| use aoc::{ | ||
| grid::{Cell, CharGrid, Grid}, | ||
| Puzzle, | ||
| }; | ||
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| struct AoC2023_21; | ||
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| impl AoC2023_21 { | ||
| fn solve(&self, grid: &CharGrid, steps: &[usize]) -> Vec<u64> { | ||
| let w = grid.width() as i32; | ||
| let start = (w / 2, w / 2); | ||
| let mut plots: HashSet<(i32, i32)> = HashSet::new(); | ||
| plots.insert(start); | ||
| let mut ans: Vec<u64> = vec![]; | ||
| for i in 1..=*steps.iter().max().unwrap() { | ||
| let mut new_plots: HashSet<(i32, i32)> = HashSet::new(); | ||
| for cell in &plots { | ||
| for (dr, dc) in [(0, 1), (0, -1), (1, 0), (-1, 0)] { | ||
| let rr = cell.0 + dr; | ||
| let cc = cell.1 + dc; | ||
| let wr = ((rr % w) + w) % w; | ||
| let wc = ((cc % w) + w) % w; | ||
| if 0 <= wr | ||
| && wr < w | ||
| && 0 <= wc | ||
| && wc < w | ||
| && grid.get(&Cell::at(wr as usize, wc as usize)) != '#' | ||
| { | ||
| new_plots.insert((rr, cc)); | ||
| } | ||
| } | ||
| } | ||
| if steps.contains(&i) { | ||
| ans.push(new_plots.len() as u64) | ||
| } | ||
| plots = new_plots; | ||
| } | ||
| ans | ||
| } | ||
| } | ||
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| impl aoc::Puzzle for AoC2023_21 { | ||
| type Input = CharGrid; | ||
| type Output1 = u64; | ||
| type Output2 = u64; | ||
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| aoc::puzzle_year_day!(2023, 21); | ||
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| fn parse_input(&self, lines: Vec<String>) -> CharGrid { | ||
| CharGrid::from(&lines.iter().map(AsRef::as_ref).collect()) | ||
| } | ||
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| fn part_1(&self, grid: &CharGrid) -> u64 { | ||
| self.solve(grid, &[64])[0] | ||
| } | ||
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| fn part_2(&self, grid: &CharGrid) -> u64 { | ||
| let steps = 26_501_365; | ||
| let modulo = steps % grid.width(); | ||
| let x: u64 = steps as u64 / grid.width() as u64; | ||
| let stepses: Vec<usize> = | ||
| (0..3).map(|i| i * grid.width() + modulo).collect(); | ||
| let values = self.solve(grid, &stepses); | ||
| let a = (values[2] + values[0] - 2 * values[1]) / 2; | ||
| let b = values[1] - values[0] - a; | ||
| let c = values[0]; | ||
| a * x * x + b * x + c | ||
| } | ||
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| fn samples(&self) { | ||
| let grid = self.parse_input(TEST.lines().map(String::from).collect()); | ||
| assert_eq!(self.solve(&grid, &[6, 10, 50, 100]), &[16, 50, 1594, 6536]); | ||
| } | ||
| } | ||
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| fn main() { | ||
| AoC2023_21 {}.run(std::env::args()); | ||
| } | ||
|
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| const TEST: &str = "\ | ||
| ........... | ||
| .....###.#. | ||
| .###.##..#. | ||
| ..#.#...#.. | ||
| ....#.#.... | ||
| .##..S####. | ||
| .##..#...#. | ||
| .......##.. | ||
| .##.#.####. | ||
| .##..##.##. | ||
| ........... | ||
| "; | ||
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| #[cfg(test)] | ||
| mod tests { | ||
| use super::*; | ||
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| #[test] | ||
| pub fn samples() { | ||
| AoC2023_21 {}.samples(); | ||
| } | ||
| } |
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