use aoc_runner_derive::{aoc, aoc_generator}; use std::collections::HashSet; #[derive(Debug, Ord, PartialOrd, Eq, PartialEq, Clone)] pub enum Inst { Acc { value: i64 }, Jmp { offset: i64 }, Nop { unused: i64 }, } #[derive(Debug, Ord, PartialOrd, Eq, PartialEq)] pub struct CPU { ip: usize, program: Vec, acc: i64, } impl Inst { fn flip(&mut self) { if let Some(new_inst) = match &self { Inst::Jmp { offset } => Some(Inst::Nop { unused: *offset }), Inst::Nop { unused } => Some(Inst::Jmp { offset: *unused }), _ => None, } { *self = new_inst; }; } } impl From<&str> for Inst { fn from(inst: &str) -> Self { let mut inst = inst.split_whitespace(); let (inst, arg) = ( inst.next().unwrap(), inst.next().map(|v| v.parse::().unwrap()), ); match inst { "jmp" => Inst::Jmp { offset: arg.unwrap(), }, "acc" => Inst::Acc { value: arg.unwrap(), }, "nop" => Inst::Nop { unused: arg.unwrap(), }, other => panic!("Invalid instruction: {}", other), } } } impl CPU { fn new(pgm: &Vec) -> Self { Self { ip: 0, program: pgm.clone(), acc: 0, } } fn flip(&mut self, idx: usize) { self.program[idx].flip(); } fn step(&mut self) -> bool { // println!("{}: {:?} [Acc: {}]",self.ip,inst, self.acc); match self.program.get(self.ip) { Some(Inst::Acc { value }) => { self.acc += value; } Some(Inst::Jmp { offset }) => { self.ip = ((self.ip as i64) + (offset - 1)) as usize; } Some(Inst::Nop { .. }) => (), None => { return false; } } self.ip += 1; return true; } } #[aoc_generator(day8)] pub fn input_generator(input: &str) -> Vec { input.trim().lines().map(|l| Inst::from(l.trim())).collect() } #[aoc(day8, part1)] pub fn solve_part1(input: &Vec) -> usize { let mut seen = HashSet::new(); let mut cpu = CPU::new(input); loop { seen.insert(cpu.ip); cpu.step(); if seen.contains(&cpu.ip) { break; } } return cpu.acc as usize; } #[aoc(day8, part2)] pub fn solve_part2(input: &Vec) -> usize { for (idx, inst) in input.iter().enumerate() { match inst { Inst::Nop { .. } | Inst::Jmp { .. } => { let mut seen = HashSet::new(); let mut cpu = CPU::new(input); cpu.flip(idx); loop { seen.insert(cpu.ip); if !cpu.step() { return cpu.acc as usize; }; if seen.contains(&cpu.ip) { break; } } } _ => (), } } panic!("Failed to solve part 2"); }