1 files changed, 96 insertions, 0 deletions
diff --git a/2019/src/bin/day_2.rs b/2019/src/bin/day_2.rs
new file mode 100644
index 0000000..ba9e189
--- /dev/null
+++ b/2019/src/bin/day_2.rs
@@ -0,0 +1,96 @@
+use aoc2019::*;
+use std::io;
+use std::io::prelude::*;
+use std::process;
+use structopt::StructOpt;
+
+#[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: 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();
+
+    match (opt.noun, opt.verb, opt.output) {
+        (Some(noun), Some(verb), _) => {
+            let result = exit_on_failed_assertion(
+                program
+                    .with_noun_verb_input(noun, verb)
+                    .execute_returning_memory_0(),
+                "Program errored",
+            );
+            println!("{}", result);
+        }
+        (_, _, Some(output)) => {
+            let (noun, verb) =
+                exit_on_failed_assertion(find_input(&program, output), "Program errored");
+            println!("({}, {})", noun, verb);
+        }
+        (None, None, None) => {
+            let result =
+                exit_on_failed_assertion(program.execute_returning_memory_0(), "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);
+        }
+    }
+}
+
+fn find_input(
+    program: &IntcodeProgram,
+    output: Intcode,
+) -> Result<(Intcode, Intcode), IntcodeProgramError> {
+    (0..99)
+        .flat_map(|noun| (0..99).map(move |verb| (Intcode::from(noun), Intcode::from(verb))))
+        .map(|(noun, verb)| {
+            (
+                noun.clone(),
+                verb.clone(),
+                program
+                    .with_noun_verb_input(noun, verb)
+                    .execute_returning_memory_0(),
+            )
+        })
+        .find(|(_noun, _verb, out)| *out == Ok(output.clone()))
+        .map(|(noun, verb, _out)| Ok((noun, verb)))
+        .unwrap_or(Err(IntcodeProgramError::Unknown))
+}