79 lines
2.1 KiB
Rust
79 lines
2.1 KiB
Rust
use std::collections;
|
|
use std::fs;
|
|
use std::io::{self, BufRead};
|
|
|
|
#[derive(Clone)]
|
|
enum Op {
|
|
Nop(i64),
|
|
Jmp(i64),
|
|
Acc(i64),
|
|
}
|
|
|
|
struct Cpu {
|
|
ip: u64,
|
|
acc: i64,
|
|
}
|
|
|
|
impl Cpu {
|
|
fn step(&mut self, code: &Vec<Op>) {
|
|
match code[self.ip as usize] {
|
|
Op::Nop(_) => {},
|
|
Op::Jmp(i) => { self.ip = (self.ip as i64 + i) as u64; return }
|
|
Op::Acc(i) => { self.acc += i }
|
|
}
|
|
self.ip += 1;
|
|
}
|
|
}
|
|
|
|
fn main() {
|
|
let file = fs::File::open("day8.txt").unwrap();
|
|
let lines: Vec<String> = io::BufReader::new(file).lines().map(|r| r.unwrap()).collect();
|
|
let mut code: Vec<Op> = lines.iter().map(|line| {
|
|
let inst: Vec<&str> = line.splitn(2, " ").collect();
|
|
match inst[0] {
|
|
"nop" => Op::Nop(inst[1].parse::<i64>().unwrap()),
|
|
"jmp" => Op::Jmp(inst[1].parse::<i64>().unwrap()),
|
|
"acc" => Op::Acc(inst[1].parse::<i64>().unwrap()),
|
|
unk => panic!("Unknown op '{}'", unk),
|
|
}
|
|
}).collect();
|
|
|
|
// Part 1.
|
|
let mut visited: collections::HashSet<u64> = collections::HashSet::new();
|
|
let mut cpu = Cpu { ip: 0, acc: 0 };
|
|
while !visited.contains(&cpu.ip) {
|
|
visited.insert(cpu.ip);
|
|
cpu.step(&code);
|
|
}
|
|
println!("Acc after first revisit: {}.", cpu.acc);
|
|
|
|
// Part 2.
|
|
for i in 0..code.len() {
|
|
match &code[i] {
|
|
Op::Jmp(val) => {
|
|
let op_backup = code[i].clone();
|
|
code[i] = Op::Nop(*val);
|
|
if let Some(acc) = run(&code) {
|
|
println!("Acc after non-looping execution: {}.", acc);
|
|
break
|
|
}
|
|
code[i] = op_backup;
|
|
}
|
|
_ => {}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn run(code: &Vec<Op>) -> Option<i64> {
|
|
let mut visited: collections::HashSet<u64> = collections::HashSet::new();
|
|
let mut cpu = Cpu { ip: 0, acc: 0 };
|
|
while cpu.ip < code.len() as u64 {
|
|
visited.insert(cpu.ip);
|
|
cpu.step(&code);
|
|
if visited.contains(&cpu.ip) {
|
|
return None
|
|
}
|
|
}
|
|
Some(cpu.acc)
|
|
}
|