From 5c7ada174a9db3a5ec98efd2d2b6840b7572e9fd Mon Sep 17 00:00:00 2001
From: kageru <kageru@encode.moe>
Date: Fri, 27 Dec 2019 12:41:59 +0100
Subject: [PATCH] Add D21P2

---
 2019/21/Cargo.toml  |  1 +
 2019/21/src/main.rs | 51 ++++++++++++++++++++++++++++++++++++---------
 2 files changed, 42 insertions(+), 10 deletions(-)

diff --git a/2019/21/Cargo.toml b/2019/21/Cargo.toml
index d18cbfd..83b2c3e 100644
--- a/2019/21/Cargo.toml
+++ b/2019/21/Cargo.toml
@@ -8,3 +8,4 @@ edition = "2018"
 
 [dependencies]
 intcode = { path = "../intcode" }
+itertools = "0.8.2"
diff --git a/2019/21/src/main.rs b/2019/21/src/main.rs
index 1214db2..7d368db 100644
--- a/2019/21/src/main.rs
+++ b/2019/21/src/main.rs
@@ -1,21 +1,52 @@
 use intcode::*;
+use itertools::Itertools;
 
-fn main() {
-    let program = "NOT A J
+// If any of the next 3 are a gap, jump
+const PART1_PROGRAM: &str = "NOT A J
 NOT B T
 OR T J
 NOT C T
 OR T J
+// unless 4 is also a gap (otherwise we’d jump right into the hole)
 AND D J
 WALK
-"
-    .chars()
-    .map(|c| c as i64)
-    .rev()
-    .collect();
-    let part1 = IntComputer::new(read_input(), 0, program)
+";
+
+const PART2_PROGRAM: &str = "NOT T T
+// if any of [A, B, C] are false, T will be false as well
+AND A T
+AND B T
+AND C T
+// jump if that is the case
+NOT T J
+// don’t jump if D (where we would land) is false
+AND D J
+// don’t jump if H is false (because that would prevent us from jumping again after we land)
+OR H T
+// unless E is true (which gives us the option to walk another step after landing)
+OR E T
+AND T J
+RUN
+";
+
+/// Remove comments and convert the source code to ASCII for the springbot.
+fn compile(program: &str) -> Vec<i64> {
+    (program.lines().filter(|l| !l.starts_with("//")).join("\n") + "\n")
+        .chars()
+        .map(|c| c as i64)
+        .rev()
+        .collect()
+}
+
+fn run(input: &Vec<i64>, program: &str) -> i64 {
+    IntComputer::new(input.clone(), 0, compile(program))
         .get_all_outputs()
         .pop()
-        .unwrap();
-    println!("{}", part1);
+        .unwrap()
+}
+
+fn main() {
+    let input = read_input();
+    println!("Part 1: {}", run(&input, PART1_PROGRAM));
+    println!("Part 2: {}", run(&input, PART2_PROGRAM));
 }