2015: day03: finish

aoc2015/src/day03.rs

@@ -0,0 +1,98 @@
+use std::collections::HashSet;
+
+use aoc::err;
+use aoc::Result;
+
+const INPUT: &str = include_str!("../input/day03.txt");
+
+pub fn run() -> Result<()> {
+    println!("part 1: {}", part1(INPUT)?);
+    println!("part 2: {}", part2(INPUT)?);
+
+    Ok(())
+}
+
+fn part1(input: &str) -> Result<usize> {
+    let mut houses = HashSet::new();
+
+    let mut x = 0;
+    let mut y = 0;
+
+    houses.insert((x, y));
+
+    for c in input.trim_end().chars() {
+        match c {
+            '>' => x += 1,
+            '<' => x -= 1,
+            '^' => y -= 1,
+            'v' => y += 1,
+            _ => return Err(err!("unidentified move: `{}`", c)),
+        }
+
+        houses.insert((x, y));
+    }
+
+    Ok(houses.len())
+}
+
+fn part2(input: &str) -> Result<usize> {
+    let mut houses = HashSet::new();
+
+    let mut santa_x = 0;
+    let mut santa_y = 0;
+
+    let mut robot_x = 0;
+    let mut robot_y = 0;
+
+    houses.insert((0, 0));
+
+    for (i, c) in input.trim_end().chars().enumerate() {
+        if i % 2 == 0 {
+            match c {
+                '>' => santa_x += 1,
+                '<' => santa_x -= 1,
+                '^' => santa_y -= 1,
+                'v' => santa_y += 1,
+                _ => return Err(err!("unidentified move: `{}`", c)),
+            }
+
+            houses.insert((santa_x, santa_y));
+        } else {
+            match c {
+                '>' => robot_x += 1,
+                '<' => robot_x -= 1,
+                '^' => robot_y -= 1,
+                'v' => robot_y += 1,
+                _ => return Err(err!("unidentified move: `{}`", c)),
+            }
+
+            houses.insert((robot_x, robot_y));
+        }
+    }
+
+    Ok(houses.len())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_provided() {
+        assert_eq!(part1(">").unwrap(), 2);
+        assert_eq!(part1("^>v<").unwrap(), 4);
+        assert_eq!(part1("^v^v^v^v^v").unwrap(), 2);
+    }
+
+    #[test]
+    fn part1_real() {
+        assert_eq!(part1(INPUT).unwrap(), 2565);
+    }
+
+    #[test]
+    fn part2_provided() {
+        assert_eq!(part2("^v").unwrap(), 3);
+        assert_eq!(part2("^>v<").unwrap(), 3);
+        assert_eq!(part2("^v^v^v^v^v").unwrap(), 11);
+    }
+}

aoc2015/src/lib.rs

@@ -1,2 +1,3 @@
 pub mod day01;
 pub mod day02;
+pub mod day03;

aoc2015/src/main.rs

@@ -2,9 +2,10 @@ use aoc::Result;
 
 use aoc2015::day01;
 use aoc2015::day02;
+use aoc2015::day03;
 
 fn main() -> Result<()> {
-    let days: &[fn() -> Result<()>] = &[day01::run, day02::run];
+    let days: &[fn() -> Result<()>] = &[day01::run, day02::run, day03::run];
 
     aoc::run(days)
 }