Finished day 3

src/day3.rs

@@ -0,0 +1,82 @@
+use std::collections::HashSet;
+use std::fs;
+
+#[derive(PartialEq, Eq, Hash, Copy, Clone, Debug)]
+pub struct Point {
+    x: isize,
+    y: isize,
+}
+
+impl Point {
+    pub fn new(x: isize, y: isize) -> Self {
+        Self { x, y }
+    }
+
+    pub fn next_point(&mut self, dir: char) {
+        match dir {
+            '^' => self.y += 1,
+            '>' => self.x += 1,
+            'v' => self.y -= 1,
+            '<' => self.x -= 1,
+            _ => (),
+        };
+    }
+}
+
+pub fn run() {
+    println!("Day 3:");
+    let input = fs::read_to_string("./inputs/day3.txt").expect("Could not read file");
+
+    println!("\tPart 1: {}", part1(&input));
+    println!("\tPart 2: {}", part2(&input));
+}
+
+fn part1(directions: &String) -> usize {
+    let mut location = Point::new(0, 0);
+    let mut prev_locs = HashSet::new();
+    prev_locs.insert(location.clone());
+
+    for dir in directions.chars() {
+        location.next_point(dir);
+        prev_locs.insert(location.clone());
+    }
+
+    return prev_locs.len();
+}
+
+fn part2(directions: &String) -> usize {
+    let mut santa = Point::new(0, 0);
+    let mut robo = Point::new(0, 0);
+    let mut prev_locs = HashSet::new();
+    prev_locs.insert(santa.clone());
+
+    for (i, dir) in directions.chars().enumerate() {
+        if i % 2 == 0 {
+            santa.next_point(dir);
+            prev_locs.insert(santa.clone());
+        } else {
+            robo.next_point(dir);
+            prev_locs.insert(robo.clone());
+        }
+    }
+
+    return prev_locs.len();
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_1() {
+        assert_eq!(part1(&">".to_string()), 2);
+        assert_eq!(part1(&"^>v<".to_string()), 4);
+        assert_eq!(part1(&"^v^v^v^v^v".to_string()), 2);
+    }
+    #[test]
+    fn test_part_2() {
+        assert_eq!(part2(&">>".to_string()), 2);
+        assert_eq!(part2(&"^>v<".to_string()), 3);
+        assert_eq!(part2(&"^v^v^v^v^v".to_string()), 11);
+    }
+}

src/main.rs

@@ -1,8 +1,10 @@
 mod day1;
 mod day2;
+mod day3;
 
 fn main() {
     println!("Running Advent of Code 2021");
     day1::run();
     day2::run();
+    day3::run();
 }