aoc/year2015/
day06.rs

1//! # Probably a Fire Hazard
2//!
3//! Brute force approach that calculates each row independently, parallelizing the work across
4//! multiple threads.
5use crate::util::iter::*;
6use crate::util::parse::*;
7use crate::util::thread::*;
8
9#[derive(Clone, Copy)]
10enum Command {
11    On,
12    Off,
13    Toggle,
14}
15
16impl Command {
17    fn from(bytes: &[u8]) -> Self {
18        match bytes[6] {
19            b'n' => Self::On,
20            b'f' => Self::Off,
21            _ => Self::Toggle,
22        }
23    }
24}
25
26#[derive(Clone, Copy)]
27pub struct Instruction {
28    command: Command,
29    x1: usize,
30    x2: usize,
31    y1: usize,
32    y2: usize,
33}
34
35impl Instruction {
36    /// Add one to both x2 and y2 to make ranges easier.
37    fn from((bytes, [x1, y1, x2, y2]): (&[u8], [usize; 4])) -> Self {
38        Self { command: Command::from(bytes), x1, x2: x2 + 1, y1, y2: y2 + 1 }
39    }
40}
41
42pub fn parse(input: &str) -> Vec<Instruction> {
43    let first = input.lines().map(str::as_bytes);
44    let second = input.iter_unsigned().chunk::<4>();
45    first.zip(second).map(Instruction::from).collect()
46}
47
48pub fn part1(input: &[Instruction]) -> u32 {
49    let items: Vec<_> = (0..1000).collect();
50    spawn_parallel_iterator(&items, |iter| worker_one(input, iter)).into_iter().sum()
51}
52
53pub fn part2(input: &[Instruction]) -> u32 {
54    let items: Vec<_> = (0..1000).collect();
55    spawn_parallel_iterator(&items, |iter| worker_two(input, iter)).into_iter().sum()
56}
57
58fn worker_one(input: &[Instruction], iter: ParIter<'_, usize>) -> u32 {
59    iter.map(|row| {
60        let mut grid = [0_u8; 1_024];
61
62        for &Instruction { command, x1, x2, y1, y2 } in input {
63            if (y1..y2).contains(row) {
64                let iter = grid[x1..x2].iter_mut();
65                match command {
66                    Command::On => iter.for_each(|b| *b = 1),
67                    Command::Off => iter.for_each(|b| *b = 0),
68                    Command::Toggle => iter.for_each(|b| *b ^= 1),
69                }
70            }
71        }
72
73        grid.into_iter().map(u32::from).sum::<u32>()
74    })
75    .sum()
76}
77
78fn worker_two(input: &[Instruction], iter: ParIter<'_, usize>) -> u32 {
79    iter.map(|row| {
80        let mut grid = [0_u8; 1_024];
81
82        for &Instruction { command, x1, x2, y1, y2 } in input {
83            if (y1..y2).contains(row) {
84                let iter = grid[x1..x2].iter_mut();
85                match command {
86                    Command::On => iter.for_each(|b| *b += 1),
87                    Command::Off => iter.for_each(|b| *b = b.saturating_sub(1)),
88                    Command::Toggle => iter.for_each(|b| *b += 2),
89                }
90            }
91        }
92
93        grid.into_iter().map(u32::from).sum::<u32>()
94    })
95    .sum()
96}
aoc/year2015/day06.rs

aoc/year2015/
day06.rs
