1 files changed, 73 insertions, 0 deletions
diff --git a/src/bin/2021/day2.rs b/src/bin/2021/day2.rs
new file mode 100644
index 0000000..5ae3596
--- /dev/null
+++ b/src/bin/2021/day2.rs
@@ -0,0 +1,73 @@
+use advent_of_code::prelude::*;
+
+pub enum Command {
+    Forward(i64),
+    Down(i64),
+    Up(i64),
+}
+
+pub fn parse(fh: File) -> Result<impl Iterator<Item = Command>> {
+    Ok(parse::raw_lines(fh).map(|line| {
+        if let Some(n) = line.strip_prefix("forward ") {
+            Command::Forward(n.parse().unwrap())
+        } else if let Some(n) = line.strip_prefix("down ") {
+            Command::Down(n.parse().unwrap())
+        } else if let Some(n) = line.strip_prefix("up ") {
+            Command::Up(n.parse().unwrap())
+        } else {
+            panic!("couldn't parse line: {}", line);
+        }
+    }))
+}
+
+pub fn part1(commands: impl Iterator<Item = Command>) -> Result<i64> {
+    let mut horizontal = 0;
+    let mut vertical = 0;
+    for command in commands {
+        match command {
+            Command::Forward(n) => {
+                horizontal += n;
+            }
+            Command::Down(n) => {
+                vertical += n;
+            }
+            Command::Up(n) => {
+                vertical -= n;
+            }
+        }
+    }
+    Ok(horizontal * vertical)
+}
+
+pub fn part2(commands: impl Iterator<Item = Command>) -> Result<i64> {
+    let mut aim = 0;
+    let mut horizontal = 0;
+    let mut vertical = 0;
+    for command in commands {
+        match command {
+            Command::Forward(n) => {
+                horizontal += n;
+                vertical += aim * n;
+            }
+            Command::Down(n) => {
+                aim += n;
+            }
+            Command::Up(n) => {
+                aim -= n;
+            }
+        }
+    }
+    Ok(horizontal * vertical)
+}
+
+#[test]
+fn test() {
+    assert_eq!(
+        part1(parse(parse::data(2021, 2).unwrap()).unwrap()).unwrap(),
+        1694130
+    );
+    assert_eq!(
+        part2(parse(parse::data(2021, 2).unwrap()).unwrap()).unwrap(),
+        1698850445
+    );
+}