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optimize 2023/10/2

This commit is contained in:
kageru 2023-12-18 15:53:14 +01:00
parent 3d75d43136
commit 5b581eeb73
1 changed files with 6 additions and 22 deletions
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28
2023/src/bin/day10.rs
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@ -6,8 +6,7 @@ use aoc2023::{
direction::{Direction, ALL_DIRECTIONS}, direction::{Direction, ALL_DIRECTIONS},
position::{Position2D, PositionND}, position::{Position2D, PositionND},
}; };
use fnv::FnvHashSet as HashSet; use itertools::Itertools;
use itertools::{Itertools, MinMaxResult};
use std::mem::transmute; use std::mem::transmute;
const DAY: usize = 10; const DAY: usize = 10;
@ -87,11 +86,11 @@ fn part2((start, grid): &Parsed) -> usize {
let mut corners = Vec::new(); let mut corners = Vec::new();
let mut dir = Direction::Down; // I got this from my part 1 solution. let mut dir = Direction::Down; // I got this from my part 1 solution.
let mut pos = *start; let mut pos = *start;
let mut points = HashSet::default(); let mut points = 0;
loop { loop {
pos = step(pos, dir); pos = step(pos, dir);
let pipe = grid[pos.0[1] as usize][pos.0[0] as usize]; let pipe = grid[pos.0[1] as usize][pos.0[0] as usize];
points.insert(pos); points += 1;
if matches!(pipe, Pipe::Start | Pipe::TopLeft | Pipe::TopRight | Pipe::BottomLeft | Pipe::BottomRight) { if matches!(pipe, Pipe::Start | Pipe::TopLeft | Pipe::TopRight | Pipe::BottomLeft | Pipe::BottomRight) {
corners.push(pos); corners.push(pos);
} }
@ -100,26 +99,11 @@ fn part2((start, grid): &Parsed) -> usize {
} }
dir = *pipe.openings().iter().find(|&&o| o != !dir).unwrap(); dir = *pipe.openings().iter().find(|&&o| o != !dir).unwrap();
} }
let MinMaxResult::MinMax(&ymin, &ymax) = corners.iter().map(|PositionND([y, _])| y).minmax() else { unreachable!() }; (2 * area(&corners) as usize - points + 2) / 2
let MinMaxResult::MinMax(&xmin, &xmax) = corners.iter().map(|PositionND([_, x])| x).minmax() else { unreachable!() };
(ymin..=ymax)
.flat_map(|y| (xmin..=xmax).map(move |x| PositionND([x, y])))
.filter(|p| !points.contains(p))
.filter(|p| is_inside(p, &corners))
.count()
} }
// A reimplementation of https://www.eecs.umich.edu/courses/eecs380/HANDOUTS/PROJ2/InsidePoly.html fn area(polygon: &[Pos]) -> isize {
fn is_inside(p: &Pos, polygon: &[Pos]) -> bool { polygon.iter().zip(polygon.iter().cycle().skip(1)).map(|(p1, p2)| p1[0] * p2[1] - p1[1] * p2[0]).sum::<isize>().abs() >> 1
// Zip with next and wrap for the last element
polygon
.iter()
.zip(polygon.iter().cycle().skip(1))
.filter(|(p1, p2)| p[1] > p1[1].min(p2[1]) && p[1] <= p1[1].max(p2[1]) && p[0] <= p1[0].max(p2[0]) && p1[1] != p2[1])
.filter(|(p1, p2)| p1[0] == p2[0] || p[0] <= (p[1] - p1[1]) * (p2[0] - p1[0]) / (p2[1] - p1[1]) + p1[0])
.count()
& 1
== 1
} }
boilerplate! { boilerplate! {