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Implement day 20.

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Bert Peters
2018-12-20 14:21:20 +01:00
parent 1424c5bfbd
commit 1355a05d2c
4 changed files with 191 additions and 27 deletions
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3
2018/benches/days.rs
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@@ -71,8 +71,9 @@ day_bench!(day16, 16);
day_bench!(day17, 17);
day_bench!(day18, 18);
day_bench!(day19, 19);
day_bench!(day20, 20);
benchmark_main!(day01, day02, day03, day04, day05,
day06, day07, day08, day09, day10,
day11, day12, day13, day14, day15,
day16, day17, day18, day19);
day16, day17, day18, day19, day20);

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2018/inputs/20.txt Normal file
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2018/loc.svg
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174
2018/src/day20.rs
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@@ -1,25 +1,187 @@
use std::collections::HashMap;
use std::collections::VecDeque;
use std::io::Read;
use common::Solution;
type Coordinate = (i32, i32);
#[derive(Copy, Clone)]
enum Direction {
North,
South,
West,
East,
}
impl Direction {
pub fn walk(self, (x, y): Coordinate) -> Coordinate {
use self::Direction::*;
match self {
North => (x, y - 1),
West => (x - 1, y),
South => (x, y + 1),
East => (x + 1, y),
}
}
}
impl From<usize> for Direction {
fn from(idx: usize) -> Self {
use self::Direction::*;
match idx {
0 => North,
1 => South,
2 => West,
3 => East,
val => panic!("Invalid direction: {}", val),
}
}
}
impl From<u8> for Direction {
fn from(b: u8) -> Self {
use self::Direction::*;
match b {
b'N' => North,
b'S' => South,
b'W' => West,
b'E' => East,
val => panic!("Invalid direction: {}", val),
}
}
}
#[derive(Default)]
pub struct Day20 {}
pub struct Day20 {
paths: HashMap<Coordinate, [bool; 4]>,
}
impl Day20 {
pub fn new() -> Self {
Default::default()
}
fn follow_directions(&mut self, initial: &[Coordinate], data: &[u8]) -> (Vec<Coordinate>, usize) {
let mut pos = Vec::from(initial);
let mut positions = Vec::new();
let mut index = 0;
while index < data.len() {
let b = data[index];
match b {
b'|' => {
positions.extend_from_slice(&pos);
pos = Vec::from(initial);
}
b'$' | b')' => {
positions.extend_from_slice(&pos);
positions.sort_unstable();
positions.dedup();
return (positions, index);
}
b'(' => {
let (new_pos, read) = self.follow_directions(&pos, &data[index + 1..]);
pos = new_pos;
index += read + 1;
}
b'N' | b'S' | b'W' | b'E' => {
let dir = Direction::from(b);
for p in pos.iter_mut() {
let entry = self.paths.entry(*p).or_insert([false; 4]);
entry[dir as usize] = true;
*p = dir.walk(*p);
}
}
val => panic!("Invalid input character: {}", val)
}
index += 1;
}
unreachable!();
}
fn distances(&self) -> HashMap<Coordinate, usize> {
let mut todo = VecDeque::new();
let mut visited = HashMap::new();
todo.push_back((0, (0, 0)));
visited.insert((0, 0), 0);
while let Some((dist, pos)) = todo.pop_front() {
if let Some(dirs) = self.paths.get(&pos) {
let dirs = dirs.iter().enumerate()
.filter_map(|(idx, state)| if *state {
Some(Direction::from(idx))
} else {
None
});
for dir in dirs {
let new_pos = dir.walk(pos);
if !visited.contains_key(&new_pos) {
visited.insert(new_pos, dist + 1);
todo.push_back((dist + 1, new_pos));
}
}
}
}
visited
}
}
impl Solution for Day20 {
fn part1(&mut self, _input: &mut Read) -> String {
unimplemented!()
fn part1(&mut self, input: &mut Read) -> String {
let mut data = Vec::new();
input.read_to_end(&mut data).unwrap();
let pos = (0, 0);
self.follow_directions(&[pos], &data[1..]);
format!("{}", self.distances().values().max().unwrap())
}
fn part2(&mut self, _input: &mut Read) -> String {
unimplemented!()
fn part2(&mut self, input: &mut Read) -> String {
let mut data = Vec::new();
input.read_to_end(&mut data).unwrap();
let pos = (0, 0);
self.follow_directions(&[pos], &data[1..]);
format!("{}", self.distances().values().filter(|&&x| x >= 1000).count())
}
}
#[cfg(test)]
mod tests {}
mod tests {
use common::Solution;
use super::*;
#[test]
fn sane_enums() {
for idx in 0..4 {
let direction = Direction::from(idx);
let back = direction as usize;
assert_eq!(idx, back);
}
}
#[test]
fn sample_part1() {
let samples: [&[u8]; 5] = [
b"^WNE$",
b"^ENWWW(NEEE|SSE(EE|N))$",
b"^ENNWSWW(NEWS|)SSSEEN(WNSE|)EE(SWEN|)NNN$",
b"^ESSWWN(E|NNENN(EESS(WNSE|)SSS|WWWSSSSE(SW|NNNE)))$",
b"^WSSEESWWWNW(S|NENNEEEENN(ESSSSW(NWSW|SSEN)|WSWWN(E|WWS(E|SS))))$",
];
let outputs = ["3", "10", "18", "23", "31"];
for (input, output) in samples.iter().zip(outputs.iter()) {
println!("{}", String::from_utf8_lossy(input));
let mut instance = Day20::new();
assert_eq!(*output, instance.part1(&mut input.as_ref()));
}
}
}