154 lines
4.1 KiB
Rust
154 lines
4.1 KiB
Rust
use std::fs::read_to_string;
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use itertools::Itertools;
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use crate::utils::grid::Grid;
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pub fn day_main() {
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let input = read_to_string("input/day14.txt").unwrap();
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let input = input.trim();
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println!(" part1: {}", part1(input));
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println!(" part2: {}", part2(input));
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}
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type RiddleResult = usize;
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fn part1(input: &str) -> RiddleResult {
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solve_part1(input, 100, 101, 103)
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}
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fn solve_part1(input: &str, rounds: i64, width: i64, height: i64) -> RiddleResult {
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let mut robots = parse(input);
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for _ in 0..rounds {
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robots.iter_mut().for_each(|((px, py), (vx, vy))| {
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*px = (*px + width + *vx) % width;
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*py = (*py + height + *vy) % height;
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});
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}
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let upper_left = robots
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.iter()
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.filter(|&&((px, py), _)| px < width / 2 && py < height / 2)
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.count();
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let lower_left = robots
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.iter()
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.filter(|&&((px, py), _)| px < width / 2 && py > height / 2)
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.count();
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let upper_right = robots
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.iter()
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.filter(|&&((px, py), _)| px > width / 2 && py < height / 2)
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.count();
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let lower_right = robots
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.iter()
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.filter(|&&((px, py), _)| px > width / 2 && py > height / 2)
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.count();
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upper_left * lower_left * upper_right * lower_right
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}
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fn parse(input: &str) -> Vec<((i64, i64), (i64, i64))> {
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input
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.lines()
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.map(|line| {
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line.strip_prefix("p=")
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.unwrap()
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.split(" v=")
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.map(|s| {
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s.split(",")
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.map(|d| d.parse::<i64>().unwrap())
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.collect_tuple::<(i64, i64)>()
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.unwrap()
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})
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.collect_tuple()
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.unwrap()
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})
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.collect_vec()
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}
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#[allow(unused)]
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fn part2(input: &str) -> i64 {
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let width = 101;
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let height = 103;
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let mut robots = parse(input);
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let max_seconds = width * height;
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for second in 0.. {
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if second > max_seconds {
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panic!("Seen all combinations but no christmas tree. So sad!");
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}
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let mut grid: Grid<u8> = Grid::from_default(101, 103);
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robots.iter_mut().for_each(|((px, py), (vx, vy))| {
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*px = (*px + width + *vx) % width;
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*py = (*py + height + *vy) % height;
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grid[(*px, *py)] += 1;
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if let Some(v) = grid.get_mut((*px + 1, *py)) {
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*v += 1
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}
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if let Some(v) = grid.get_mut((*px - 1, *py)) {
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*v += 1
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}
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if let Some(v) = grid.get_mut((*px, *py + 1)) {
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*v += 1
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}
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if let Some(v) = grid.get_mut((*px, *py - 1)) {
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*v += 1
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}
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});
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if robots.iter().filter(|(s, _)| grid[*s] > 1).count() > robots.len() * 70 / 100 {
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// printr(&robots, width, height);
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// println!("after {} seconds. Press enter to continue or type 'merry christmas' if you can spot a tree!", second + 1); //+1 because we look at it after they have changed
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return second + 1;
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// let stdin = io::stdin();
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// let line = stdin.lock().lines().next().unwrap().unwrap();
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// if line.as_str().eq_ignore_ascii_case("merry christmas") {
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// return second + 1;
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// }
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}
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}
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unreachable!()
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}
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#[allow(unused)]
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type Robot = ((i64, i64), (i64, i64));
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#[allow(unused)]
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fn printr(robots: &[Robot], width: i64, height: i64) {
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for y in 0..height {
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for x in 0..width {
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let c = robots
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.iter()
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.filter(|&&((px, py), _)| px == x && py == y)
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.count();
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if c == 0 {
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print!(".");
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} else {
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print!("{c}");
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}
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}
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println!();
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}
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}
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#[cfg(test)]
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mod test {
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use crate::day14::solve_part1;
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const TEST_INPUT: &str = r"p=0,4 v=3,-3
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p=6,3 v=-1,-3
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p=10,3 v=-1,2
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p=2,0 v=2,-1
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p=0,0 v=1,3
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p=3,0 v=-2,-2
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p=7,6 v=-1,-3
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p=3,0 v=-1,-2
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p=9,3 v=2,3
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p=7,3 v=-1,2
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p=2,4 v=2,-3
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p=9,5 v=-3,-3
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";
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#[test]
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fn test1() {
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assert_eq!(solve_part1(TEST_INPUT, 100, 11, 7), 12);
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}
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}
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