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use {
anyhow::{
anyhow,
Context,
Result,
},
regex::Regex,
std::{
env::args,
fs::File,
io::{
BufRead,
BufReader,
},
path::Path,
},
};
#[derive(Clone,Copy)]
enum Instruction {
Addx(isize),
Noop,
}
impl Instruction {
fn cycles(&self) -> usize {
match self {
Instruction::Addx(_) => 2,
Instruction::Noop => 1,
}
}
}
#[derive(Clone)]
struct Program {
inner: Vec<Instruction>,
}
impl Program {
fn instruction(&self, cycle: usize) -> Option<Instruction> {
let mut counter = 0;
for instruction in self.inner.iter() {
counter += instruction.cycles();
match counter {
c if c == cycle => return Some(*instruction),
c if c > cycle => return None,
_ => { },
}
}
None
}
}
struct Registers {
x: isize,
}
impl Registers {
fn new() -> Self {
Self {
x: 1,
}
}
}
struct Cpu {
cycle: usize,
program: Program,
registers: Registers,
}
impl Cpu {
fn new(program: Program) -> Self {
let registers = Registers::new();
Self {
cycle: 0,
program,
registers,
}
}
fn step(&mut self) {
if let Some(instruction) = self.program.instruction(self.cycle) {
match instruction {
Instruction::Addx(argument) => self.registers.x += argument,
Instruction::Noop => { },
}
}
self.cycle += 1;
}
fn signal_strength(&self) -> isize {
self.registers.x * self.cycle as isize
}
fn pixel(&self) -> String {
if ((self.registers.x - 1)..=(self.registers.x + 1))
.contains(&((self.cycle - 1) as isize % 40))
{
String::from("#")
} else {
String::from(".")
}
}
}
fn read_input<T: AsRef<Path>>(filename: T) -> Result<Program> {
let reader = BufReader::new(File::open(filename)?);
let re = Regex::new(r#"(?x)^
(?P<instruction>(addx)|(noop))
(
\s
(?P<argument>[0-9-]+)
)?
$"#)?;
let instructions = reader.lines().map(
|v| {
let s = v?;
let caps = re.captures(&s).ok_or_else(|| anyhow!("Could not parse: {s}"))?;
let instruction = caps.name("instruction").unwrap_or_else(|| unreachable!()).as_str();
let argument = caps.name("argument").map(|a| a.as_str()).unwrap_or_default();
match instruction {
"addx" => Ok(Instruction::Addx(argument.parse()?)),
"noop" => Ok(Instruction::Noop),
_ => unreachable!(),
}
}
).collect::<Result<Vec<_>>>()?;
Ok(Program { inner: instructions })
}
fn part1(input: &Program) -> Result<isize> {
let mut cpu = Cpu::new(input.clone());
let mut sum = 0;
for i in 0..=220 {
if [20, 60, 100, 140, 180, 220].contains(&i) {
sum += cpu.signal_strength();
}
cpu.step();
}
Ok(sum)
}
fn part2(input: &Program) -> Result<String> {
let mut cpu = Cpu::new(input.clone());
let mut output = String::default();
for i in 0..240 {
cpu.step();
if i % 40 == 0 {
output += "\n";
}
output += &cpu.pixel();
}
Ok(output)
}
fn main() -> Result<()> {
let ( do_part_1, do_part_2 ) = aoc::do_parts();
let filename = args().nth(1).ok_or_else(|| anyhow!("Missing input filename"))?;
let input = read_input(filename).context("Could not read input")?;
if do_part_1 {
let solution = part1(&input).context("No solution for part 1")?;
println!("Part1, solution found to be: {}", solution);
}
if do_part_2 {
let solution = part2(&input).context("No solution for part 2")?;
println!("Part2, solution found to be: {}", solution);
}
Ok(())
}
|
