2 files changed, 106 insertions, 0 deletions
diff --git a/src/day_2.rs b/src/day_2.rs
new file mode 100644
index 0000000..d7ebcd0
--- /dev/null
+++ b/src/day_2.rs
@@ -0,0 +1,104 @@
+use std::ops::AddAssign;
+
+type Scalar = isize;
+
+#[derive(Copy, Clone, Debug)]
+enum Instruction
+{
+    Forward(Scalar),
+    Down(Scalar),
+    Up(Scalar),
+}
+
+#[derive(Copy, Clone, Debug)]
+struct Victor
+{
+    x: Scalar,
+    y: Scalar,
+}
+
+fn part1(instructions: &[Instruction])
+{
+    let directions: Vec<Victor> = instructions
+        .iter()
+        .map(|&i| Victor::from_direct_instruction(i))
+        .collect();
+
+    let mut position = Victor::new(0, 0);
+    for dir in directions {
+        position += dir;
+    }
+
+    println!("Solution to part 1: {}", position.x * position.y);
+}
+
+fn part2(instructions: &[Instruction])
+{
+    let mut aim: Scalar = 0;
+    let mut position = Victor::new(0, 0);
+
+    for i in instructions {
+        match &i {
+            Instruction::Down(amount) => aim += amount,
+            Instruction::Up(amount) => aim -= amount,
+            Instruction::Forward(amount) => position += Victor::new(*amount, amount * aim),
+        }
+    }
+
+    println!("Solution to part 2: {}", position.x * position.y);
+}
+
+pub fn run(input: Vec<String>)
+{
+    let instructions: Vec<Instruction> = input
+        .into_iter()
+        .map(|s| Instruction::from_str(s))
+        .collect();
+
+    part1(&instructions);
+    part2(&instructions);
+}
+
+impl Instruction
+{
+    pub fn from_str<S>(instruction_str: S) -> Self
+    where
+        S: AsRef<str>,
+    {
+        let parts: Vec<&str> = instruction_str.as_ref().split_whitespace().collect();
+        assert_eq!(parts.len(), 2);
+
+        let scalar = parts[1].parse().expect("Not a valid length");
+        match parts[0] {
+            "forward" => Self::Forward(scalar),
+            "down" => Self::Down(scalar),
+            "up" => Self::Up(scalar),
+            o => panic!("{} is not a valid instruction", o),
+        }
+    }
+}
+
+impl Victor
+{
+    pub fn new(x: Scalar, y: Scalar) -> Self { Self { x, y } }
+
+    pub fn from_direct_instruction(instruction: Instruction) -> Self
+    {
+        use Instruction::*;
+
+        match instruction {
+            Forward(distance) => Victor::new(distance, 0),
+            Down(distance) => Victor::new(0, distance),
+            Up(distance) => Victor::new(0, -distance),
+        }
+    }
+}
+
+impl AddAssign for Victor
+{
+    fn add_assign(&mut self, rhs: Self)
+    {
+        self.x += rhs.x;
+        self.y += rhs.y;
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index c45571e..0c3f0a7 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,5 @@
 mod day_1;
+mod day_2;
 
 use std::fs::File;
 use std::io::{BufRead, BufReader};
@@ -26,6 +27,7 @@ fn run(day: u8, input: Vec<String>)
 {
     match day {
         1 => day_1::run(input),
+        2 => day_2::run(input),
         o => panic!("Day {} is not implemented (yet)", o),
     }
 }