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use im::vector::Vector;
use std::fmt;
use std::io;
use std::io::prelude::*;
use std::iter;
use std::iter::FromIterator;
use std::iter::IntoIterator;
use std::process;
use structopt::StructOpt;
type Intcode = u32;
#[derive(Debug, StructOpt)]
#[structopt(name = "Day 2: 1202 Program Alarm")]
/// Executes an Intcode program
///
/// The program is read from stdin as a series of comma-separated
/// values. Newlines are ignored. When the program halts, the value at
/// position 0 is returned.
///
/// If an output is provided, all possible inputs are tried to find
/// the input that results in the desired output. In this case, the
/// inputs are returned in the format (noun, verb).
///
///See https://adventofcode.com/2019/day/2 for details.
struct Opt {
#[structopt(short = "n", long = "noun")]
noun: Option<Intcode>,
#[structopt(short = "v", long = "verb")]
verb: Option<Intcode>,
#[structopt(short = "o", long = "output")]
output: Option<Intcode>,
}
fn main() {
let stdin = io::stdin();
let opt = Opt::from_args();
let program: Program = stdin
.lock()
.split(b',')
.map(|x| exit_on_failed_assertion(x, "Error reading input"))
.map(|x| exit_on_failed_assertion(String::from_utf8(x), "Input was not valid UTF-8"))
.map(|x| exit_on_failed_assertion(x.trim().parse::<Intcode>(), "Invalid number"))
.collect();
match (opt.noun, opt.verb, opt.output) {
(Some(noun), Some(verb), _) => {
let result = exit_on_failed_assertion(
program.set_input(noun, verb).execute(),
"Program errored",
);
println!("{}", result);
}
(_, _, Some(output)) => {
let (noun, verb) =
exit_on_failed_assertion(program.find_input(output), "Program errored");
println!("({}, {})", noun, verb);
}
(None, None, None) => {
let result = exit_on_failed_assertion(program.execute(), "Program errored");
println!("{}", result);
}
_ => {
eprintln!("Either a noun and verb or an expected output must be provided");
process::exit(1);
}
}
}
fn exit_on_failed_assertion<A, E: std::error::Error>(data: Result<A, E>, message: &str) -> A {
match data {
Ok(data) => data,
Err(e) => {
eprintln!("{}: {}", message, e);
process::exit(1);
}
}
}
#[derive(Debug, Clone)]
struct Program {
program_counter: usize,
error: bool,
halted: bool,
codes: Vector<Intcode>,
}
impl FromIterator<Intcode> for Program {
fn from_iter<I: IntoIterator<Item = Intcode>>(iter: I) -> Self {
Program {
program_counter: 0,
error: false,
halted: false,
codes: iter.into_iter().collect(),
}
}
}
impl Program {
fn set_input(&self, noun: Intcode, verb: Intcode) -> Program {
Program {
codes: self.codes.update(1, noun).update(2, verb),
..self.clone()
}
}
fn find_input(&self, output: Intcode) -> Result<(Intcode, Intcode), ProgramError> {
(0..99)
.flat_map(|noun| (0..99).map(move |verb| (noun, verb)))
.map(|(noun, verb)| (noun, verb, self.set_input(noun, verb).execute()))
.find(|(_noun, _verb, out)| *out == Ok(output))
.map(|(noun, verb, _out)| Ok((noun, verb)))
.unwrap_or(Err(ProgramError))
}
fn execute(&self) -> Result<Intcode, ProgramError> {
self.run_to_termination().into_result()
}
fn into_result(&self) -> Result<Intcode, ProgramError> {
if self.error {
Err(ProgramError)
} else {
Ok(self.codes.head().unwrap().clone())
}
}
fn run_to_termination(&self) -> Program {
iter::successors(Some(self.clone()), |p| Some(Program::next(&p)))
.find(|p| p.halted)
.unwrap() // successors doesn't terminate, so this will never be none.
}
fn next(&self) -> Program {
//eprintln!("{:?}", self);
match self.codes.get(self.program_counter) {
Some(1) => self.add(),
Some(2) => self.multiply(),
Some(99) => self.halt(),
Some(_) => self.error(),
None => self.error(),
}
}
fn add(&self) -> Program {
match (self.get_deref(1), self.get_deref(2), self.get(3)) {
(Some(in1), Some(in2), Some(out)) => Program {
program_counter: self.program_counter + 4,
codes: self.codes.update(out as usize, in1 + in2),
..self.clone()
},
_ => self.error(),
}
}
fn multiply(&self) -> Program {
match (self.get_deref(1), self.get_deref(2), self.get(3)) {
(Some(in1), Some(in2), Some(out)) => Program {
program_counter: self.program_counter + 4,
codes: self.codes.update(out as usize, in1 * in2),
..self.clone()
},
_ => self.error(),
}
}
fn halt(&self) -> Program {
Program {
halted: true,
..self.clone()
}
}
fn error(&self) -> Program {
Program {
halted: true,
error: true,
..self.clone()
}
}
fn get(&self, pointer_offset: usize) -> Option<Intcode> {
self.codes
.get(self.program_counter + pointer_offset)
.cloned()
}
fn get_deref(&self, pointer_offset: usize) -> Option<Intcode> {
self.get(pointer_offset)
.and_then(|r| self.codes.get(r as usize))
.cloned()
}
}
#[derive(Debug, PartialEq)]
struct ProgramError;
impl fmt::Display for ProgramError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "Unknown error")
}
}
impl std::error::Error for ProgramError {}
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