112 lines
3.3 KiB
Rust
112 lines
3.3 KiB
Rust
#![warn(clippy::all, clippy::pedantic)]
|
|
|
|
use glam::DVec3;
|
|
use nom::{
|
|
bytes::complete::tag,
|
|
character::complete,
|
|
multi::separated_list1,
|
|
number,
|
|
sequence::{separated_pair, tuple},
|
|
IResult, Parser,
|
|
};
|
|
|
|
use itertools::Itertools;
|
|
|
|
#[derive(Debug, Clone, Copy)]
|
|
struct Stones {
|
|
pub start: DVec3,
|
|
pub velocity: DVec3,
|
|
}
|
|
impl Stones {
|
|
fn cross(&self, other: &Self) -> Option<DVec3> {
|
|
// x1 + v_x1 *t = x_n
|
|
// t= (x_n - x_1)/v_x1
|
|
// (y_n - y_1)/v_y1 = (x_n - x_1)/v_x1
|
|
// y_n = v_y1 * (x_n -x_1)/v_x1 + y_1
|
|
// (v_y1/v_x1) * x_n - x_1 * (v_y1/v_x1) + y_1 = (v_y2/v_x2) * x_n -x_2 * (v_y2/v_x2) + y_2
|
|
// x_n * ((v_y1/v_x1) - (v_y2/v_x2)) = x_1 * (v_y1/v_x1) - x_2 * (v_y2/v_x2) + y_2 - y_1
|
|
// x1 + v1 *t == x2 + v2*t
|
|
// (x1-x2)/(v2-v1) = t
|
|
let slope1 = self.velocity.y / self.velocity.x;
|
|
let slope2 = other.velocity.y / other.velocity.x;
|
|
let denom = slope1 - slope2;
|
|
let x =
|
|
(self.start.x * slope1 - other.start.x * slope2 + other.start.y - self.start.y) / denom;
|
|
let y = slope1 * (x - self.start.x) + self.start.y;
|
|
if !x.is_finite() || !y.is_finite() {
|
|
return None;
|
|
}
|
|
let t1 = (x - self.start.x) / self.velocity.x;
|
|
let t2 = (x - other.start.x) / other.velocity.x;
|
|
if t1 < 0.0 || t2 < 0.0 {
|
|
return None;
|
|
}
|
|
Some(DVec3::new(x, y, 0.0))
|
|
}
|
|
}
|
|
|
|
/// day 24 part 1 of aoc 2023
|
|
///
|
|
/// # Arguments
|
|
/// - input the input for today's puzzle
|
|
///
|
|
/// # Panics
|
|
/// panics whne it cannot parse the input OR when ever the number of game numbers is greater than
|
|
#[must_use]
|
|
pub fn part1(input: &str, min: f64, max: f64) -> String {
|
|
let (_, stones) = parse_input(input).expect("Aoc should have valid input");
|
|
stones
|
|
.iter()
|
|
.combinations(2)
|
|
.filter_map(|pair| {
|
|
let [a, b] = pair[..] else { return None };
|
|
a.cross(b).and_then(|cross_position| {
|
|
(cross_position.x <= max
|
|
&& cross_position.y <= max
|
|
&& cross_position.x >= min
|
|
&& cross_position.y >= min)
|
|
.then_some(cross_position)
|
|
})
|
|
})
|
|
.count()
|
|
.to_string()
|
|
}
|
|
|
|
fn parse_tuple(input: &str) -> IResult<&str, DVec3> {
|
|
let (input, x) = number::complete::double(input)?;
|
|
let (input, _) = tuple((tag(","), complete::space0))(input)?;
|
|
let (input, y) = number::complete::double(input)?;
|
|
let (input, _) = tuple((tag(","), complete::space0))(input)?;
|
|
let (input, z) = number::complete::double(input)?;
|
|
Ok((input, DVec3::new(x, y, z)))
|
|
}
|
|
|
|
fn parse_input(input: &str) -> IResult<&str, Vec<Stones>> {
|
|
separated_list1(
|
|
complete::line_ending,
|
|
separated_pair(
|
|
parse_tuple,
|
|
tuple((complete::space0, tag("@"), complete::space0)),
|
|
parse_tuple,
|
|
)
|
|
.map(|(start, velocity)| Stones { start, velocity }),
|
|
)(input)
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod test {
|
|
use super::*;
|
|
|
|
const INPUT: &str = "19, 13, 30 @ -2, 1, -2
|
|
18, 19, 22 @ -1, -1, -2
|
|
20, 25, 34 @ -2, -2, -4
|
|
12, 31, 28 @ -1, -2, -1
|
|
20, 19, 15 @ 1, -5, -3";
|
|
|
|
#[test]
|
|
fn part1_works() {
|
|
let result = part1(INPUT, 7.0, 27.0);
|
|
assert_eq!(result, "2".to_string());
|
|
}
|
|
}
|