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2022 day9/rust: abort early if knot doesn't move

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Xiretza 2022-12-09 21:36:05 +01:00
parent e1862bdcbb
commit daad18c6af
1 changed files with 12 additions and 15 deletions
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27
2022/day9/rust/src/main.rs
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@ -1,3 +1,4 @@
#![feature(iterator_try_reduce)]
#![warn(clippy::pedantic)] #![warn(clippy::pedantic)]
use std::{ use std::{
@ -7,15 +8,14 @@ use std::{
use aoc::vec2::{Direction, Vec2}; use aoc::vec2::{Direction, Vec2};
fn knot_movement(previous: Vec2, knot: Vec2) -> Vec2 { fn knot_movement(previous: Vec2, knot: Vec2) -> Option<Vec2> {
let (dx, dy) = (previous - knot).into(); let (dx, dy) = (previous - knot).into();
let movement = if dx.abs() <= 1 && dy.abs() <= 1 { if dx.abs() <= 1 && dy.abs() <= 1 {
(0, 0) None
} else { } else {
(dx.signum(), dy.signum()) Some((dx.signum(), dy.signum()).into())
}; }
movement.into()
} }
fn simulate_knots(num_knots: usize, instructions: &[(Direction, usize)]) -> usize { fn simulate_knots(num_knots: usize, instructions: &[(Direction, usize)]) -> usize {
@ -31,15 +31,12 @@ fn simulate_knots(num_knots: usize, instructions: &[(Direction, usize)]) -> usiz
for _i in 0..*distance { for _i in 0..*distance {
knots[0] += Vec2::from(*direction); knots[0] += Vec2::from(*direction);
let tail = knots if let Some(tail) = knots.iter_mut().try_reduce(|previous, knot| {
.iter_mut() *knot += knot_movement(*previous, *knot)?;
.reduce(|previous, knot| { Some(knot)
*knot += knot_movement(*previous, *knot); }) {
knot tail_positions.insert(tail.copied().unwrap());
}) }
.unwrap();
tail_positions.insert(*tail);
} }
} }