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