2 files changed, 62 insertions, 7 deletions
diff --git a/src/bin/day_17.rs b/src/bin/day_17.rs
index 9f5d3b8..e85373c 100644
--- a/src/bin/day_17.rs
+++ b/src/bin/day_17.rs
@@ -1,13 +1,6 @@
 use aoc2019::*;
-use rpds::list;
-use rpds::list::List;
-use rpds::rbt_set;
-use rpds::set::red_black_tree_set::RedBlackTreeSet;
-use rpds::vector;
-use rpds::vector::Vector;
 use std::io;
 use std::io::prelude::*;
-use std::iter;
 use std::process;
 use structopt::StructOpt;
 
diff --git a/src/bin/day_21.rs b/src/bin/day_21.rs
new file mode 100644
index 0000000..106ce82
--- /dev/null
+++ b/src/bin/day_21.rs
@@ -0,0 +1,62 @@
+use aoc2019::*;
+use std::io;
+use std::io::prelude::*;
+use std::process;
+use structopt::StructOpt;
+
+#[derive(Debug, StructOpt)]
+#[structopt(name = "Day 21: Springdroid Adventure")]
+/// Pilots a springdroid around!
+///
+/// See https://adventofcode.com/2019/day/21 for details.
+struct Opt {}
+
+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>();
+
+    let result = exit_on_failed_assertion(
+        {
+            let input = vec!["NOT A J\n", "WALK\n"];
+            program
+                .with_input(
+                    input
+                        .iter()
+                        .flat_map(|line| line.chars().map(|c| Intcode::from(c as u8)))
+                        .collect(),
+                )
+                .execute()
+        },
+        "Program failed",
+    );
+
+    println!(
+        "{}",
+        result
+            .drop_last()
+            .unwrap()
+            .iter()
+            .flat_map(|c| c.to_signed_bytes_be())
+            .map(|c| c as char)
+            .collect::<String>()
+    );
+    println!("{}", result.last().unwrap());
+}
+
+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);
+        }
+    }
+}