Implementation 2021 day 2

2021/src/day02.rs

@@ -1,9 +1,90 @@
+use std::io::BufRead;
+use std::io::BufReader;
 use std::io::Read;
 
-pub fn part1(_input: &mut dyn Read) -> String {
-    todo!()
+enum Dir {
+    Up,
+    Down,
+    Forward,
 }
 
-pub fn part2(_input: &mut dyn Read) -> String {
-    todo!()
+fn parse_input(input: &mut dyn Read) -> Vec<(Dir, i32)> {
+    let mut reader = BufReader::new(input);
+    let mut buffer = String::new();
+
+    let mut moves = Vec::new();
+
+    while matches!(reader.read_line(&mut buffer), Ok(n) if n > 0) {
+        let (dir, amount) = buffer.trim().split_once(" ").unwrap();
+
+        let dir = match dir {
+            "up" => Dir::Up,
+            "down" => Dir::Down,
+            "forward" => Dir::Forward,
+            _ => panic!("Invalid direction '{}'", dir),
+        };
+
+        moves.push((dir, amount.parse().unwrap()));
+
+        buffer.clear();
+    }
+
+    moves
+}
+
+pub fn part1(input: &mut dyn Read) -> String {
+    let moves = parse_input(input);
+
+    let mut x = 0;
+    let mut depth = 0;
+
+    for (dir, amount) in moves {
+        match dir {
+            Dir::Up => depth -= amount,
+            Dir::Down => depth += amount,
+            Dir::Forward => x += amount,
+        }
+    }
+
+    (x * depth).to_string()
+}
+
+pub fn part2(input: &mut dyn Read) -> String {
+    let moves = parse_input(input);
+
+    let mut x = 0;
+    let mut depth = 0;
+    let mut aim = 0;
+
+    for (dir, amount) in moves {
+        match dir {
+            Dir::Up => aim -= amount,
+            Dir::Down => aim += amount,
+            Dir::Forward => {
+                x += amount;
+                depth += aim * amount;
+            }
+        }
+    }
+
+    (x * depth).to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::test_implementation;
+
+    use super::*;
+
+    const SAMPLE: &[u8] = include_bytes!("samples/02.txt");
+
+    #[test]
+    fn sample_part1() {
+        test_implementation(part1, SAMPLE, 150);
+    }
+
+    #[test]
+    fn sample_part2() {
+        test_implementation(part1, SAMPLE, 150);
+    }
 }

2021/src/samples/02.txt

@@ -0,0 +1,6 @@
+forward 5
+down 5
+forward 8
+up 3
+down 8
+forward 2