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use aoc2019::*;
use cached::cached_key;
use cached::UnboundCache;
use rpds::list;
use rpds::list::List;
use rpds::vector;
use std::io;
use std::io::prelude::*;
use std::process;
use structopt::StructOpt;
#[derive(Debug, StructOpt)]
#[structopt(name = "Day 19: Tractor Beam")]
/// Finds the effective area of a tractor beam in an n x n square, and
/// how far away you need to be to capture Santa's ship.
///
/// See https://adventofcode.com/2019/day/19 for details.
struct Opt {
/// The size for a diagnostics scan.
#[structopt(long = "diagnostics-size")]
diagnostics_size: Option<usize>,
/// The size of Santa's ship
#[structopt(long = "ship-size")]
ship_size: Option<usize>,
}
fn main() {
let stdin = io::stdin();
let opt = Opt::from_args();
let program: IntcodeProgram = 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::<IntcodeProgram>();
if let Some(size) = opt.diagnostics_size {
println!("{}", count_active_in_area(program.clone(), 0, 0, size));
}
if let Some(size) = opt.ship_size {
println!("{:?}", find_closest_ship_space(program, size))
}
}
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);
}
}
}
fn count_active_in_area(program: IntcodeProgram, left: usize, top: usize, size: usize) -> usize {
(left..left + size)
.flat_map(|x| (top..top + size).map(move |y| (x, y)))
.filter(|(x, y)| tractor_beam_is_active(program.clone(), *x, *y))
.count()
}
fn area_is_all_full(program: IntcodeProgram, left: usize, top: usize, size: usize) -> bool {
// This check with a grid that's aligned to 10 gives an early exit
// for most, that will have the program executions shared. This
// makes the memoized tractor function more effective at cutting
// down on execution, even though you need to do the whole lot
// again to verify if this passes.
(left..left + size)
.flat_map(|x| (top..top + size).map(move |y| (x, y)))
.filter(|(x, y)| x % 10 == 0 && y % 10 == 0)
.all(|(x, y)| tractor_beam_is_active(program.clone(), x, y))
&& (left..left + size)
.flat_map(|x| (top..top + size).map(move |y| (x, y)))
.all(|(x, y)| tractor_beam_is_active(program.clone(), x, y))
}
fn find_closest_ship_space(program: IntcodeProgram, size: usize) -> (usize, usize) {
(0..)
.flat_map(|radius| {
(0..radius)
.flat_map(move |x| (0..radius).map(move |y| (x, y)))
.filter(move |(x, y)| {
(radius - 1) * (radius - 1) < x * x + y * y && x * x + y * y <= radius * radius
})
})
.find(|(x, y)| area_is_all_full(program.clone(), *x, *y, size))
.unwrap()
}
cached_key! {
TRACTOR_BEAM_IS_ACTIVE: UnboundCache<(usize, usize), bool> = UnboundCache::new();
Key = { (x, y) };
fn tractor_beam_is_active(program: IntcodeProgram, x: usize, y: usize) -> bool = {
program
.with_input(list![Intcode::from(x), Intcode::from(y)])
.execute()
== Ok(vector![Intcode::from(1)])
}
}
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