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)]
27struct Rectangle {
28    x1: usize,
29    x2: usize,
30    y1: usize,
31    y2: usize,
32}
33
34impl Rectangle {
35    /// Add one to both x2 and y2 to make ranges easier.
36    fn from([x1, y1, x2, y2]: [usize; 4]) -> Self {
37        Self { x1, y1, x2: x2 + 1, y2: y2 + 1 }
38    }
39}
40
41#[derive(Clone, Copy)]
42pub struct Instruction {
43    command: Command,
44    rectangle: Rectangle,
45}
46
47impl Instruction {
48    fn from((bytes, points): (&[u8], [usize; 4])) -> Self {
49        Self { command: Command::from(bytes), rectangle: Rectangle::from(points) }
50    }
51}
52
53pub fn parse(input: &str) -> Vec<Instruction> {
54    let first = input.lines().map(str::as_bytes);
55    let second = input.iter_unsigned().chunk::<4>();
56    first.zip(second).map(Instruction::from).collect()
57}
58
59pub fn part1(input: &[Instruction]) -> u32 {
60    let items: Vec<_> = (0..1000).collect();
61    let result = spawn_parallel_iterator(&items, |iter| worker_one(input, iter));
62    result.into_iter().sum()
63}
64
65pub fn part2(input: &[Instruction]) -> u32 {
66    let items: Vec<_> = (0..1000).collect();
67    let result = spawn_parallel_iterator(&items, |iter| worker_two(input, iter));
68    result.into_iter().sum()
69}
70
71fn worker_one(input: &[Instruction], iter: ParIter<'_, usize>) -> u32 {
72    iter.map(|row| {
73        let mut grid = [0_u8; 1_024];
74
75        for &Instruction { command, rectangle: Rectangle { x1, y1, x2, y2 } } in input {
76            if (y1..y2).contains(row) {
77                let iter = grid[x1..x2].iter_mut();
78                match command {
79                    Command::On => iter.for_each(|b| *b = 1),
80                    Command::Off => iter.for_each(|b| *b = 0),
81                    Command::Toggle => iter.for_each(|b| *b ^= 1),
82                }
83            }
84        }
85
86        grid.into_iter().map(|b| b as u32).sum::<u32>()
87    })
88    .sum()
89}
90
91fn worker_two(input: &[Instruction], iter: ParIter<'_, usize>) -> u32 {
92    iter.map(|row| {
93        let mut grid = [0_u8; 1_024];
94
95        for &Instruction { command, rectangle: Rectangle { x1, y1, x2, y2 } } in input {
96            if (y1..y2).contains(row) {
97                let iter = grid[x1..x2].iter_mut();
98                match command {
99                    Command::On => iter.for_each(|b| *b += 1),
100                    Command::Off => iter.for_each(|b| *b = b.saturating_sub(1)),
101                    Command::Toggle => iter.for_each(|b| *b += 2),
102                }
103            }
104        }
105
106        grid.into_iter().map(|b| b as u32).sum::<u32>()
107    })
108    .sum()
109}
aoc/year2015/day06.rs

aoc/year2015/
day06.rs
