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use anyhow::Result;
use std::convert::TryFrom;
use std::env::args;
use std::fs::File;
use std::io::{BufRead, BufReader};
use std::path::Path;
use day08::intcode::{Instruction, Intcode};
use day08::intcode;
fn read_input<T: AsRef<Path>>(filename: T) -> Result<Vec<Instruction>> {
let f = File::open(filename)?;
let reader = BufReader::new(f);
reader.lines()
.map(|v| Ok(Instruction::try_from(v?)?))
.collect()
}
fn part1(program: &[Instruction]) -> Result<intcode::Wordsize> {
let mut visited = vec![];
let mut intcode = Intcode::new();
intcode.load(program);
loop {
let registers = intcode.regdump();
if visited.contains(®isters.ip) {
return Ok(registers.accumulator);
}
visited.push(registers.ip);
intcode.step()?
}
}
fn part2(program: &[Instruction]) -> Option<intcode::Wordsize> {
'reset: for i in 0..program.len() {
let mut modified = program.to_vec();
match modified.get_mut(i) {
Some(instruction) => match instruction {
Instruction::Jmp(arg) => *instruction = Instruction::Nop(*arg),
Instruction::Nop(arg) => *instruction = Instruction::Jmp(*arg),
_ => {},
},
None => panic!("Invalid loop index"),
}
let mut visited = vec![];
let mut intcode = Intcode::new();
intcode.load(&modified);
loop {
let registers = intcode.regdump();
if visited.contains(®isters.ip) {
continue 'reset;
}
visited.push(registers.ip);
match intcode.step() {
Ok(_) => {},
Err(_) => {
// Weird as it might seem, Error is Success in this aoc case.
let registers = intcode.regdump();
return Some(registers.accumulator);
}
}
}
}
None
}
fn main() {
let (do_part_1, do_part_2) = aoc::do_parts();
let filename = match args().nth(1) {
Some(f) => f,
None => {
eprintln!("Missing input filename");
std::process::exit(1);
},
};
match read_input(filename) {
Ok(input) => {
if do_part_1 {
match part1(&input) {
Ok(solution) => println!("Part1, {}", solution),
Err(err) => eprintln!("Part1, {}", err),
}
}
if do_part_2 {
match part2(&input) {
Some(solution) => println!("Part2, {}", solution),
None => eprintln!("Part2, no solution found"),
}
}
},
Err(err) => eprintln!("Could not read input: {}", err),
}
}
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