day8 solution 1

1 files changed, 86 insertions, 0 deletions

diff --git a/src/bin/day8.rs b/src/bin/day8.rs
new file mode 100644
index 0000000..ab8595f
--- /dev/null
+++ b/src/bin/day8.rs
@@ -0,0 +1,86 @@
+use std::collections::{HashMap, HashSet};
+
+static DAY: u8 = 8;
+
+fn main() {
+    let input = advent::read_lines(DAY);
+    println!("{DAY}a: {}", Map::new(&input).count_antinodes());
+    println!("{DAY}b: {}", 0);
+}
+
+#[derive(Eq, PartialEq, Hash)]
+struct Position {
+    x: isize,
+    y: isize,
+}
+
+impl Position {
+    fn add_position(&self, other: &Position) -> Position {
+        Position { x: self.x + (self.x - other.x), y: self.y + (self.y - other.y) }
+    }
+}
+
+struct Map {
+    antennas: HashMap<Position, char>,
+    dimensions: Position,
+}
+
+impl Map {
+    fn new(input: &[String]) -> Map {
+        let mut antennas = HashMap::new();
+
+        for (y, line) in input.iter().enumerate() {
+            for (x, c) in line.chars().enumerate() {
+                if c != '.' {
+                    let pos = Position { x: x as isize, y: y as isize };
+                    antennas.insert(pos, c);
+                }
+            }
+        }
+        let dimensions = Position { x: input[0].len() as isize, y: input.len() as isize };
+        Map { antennas, dimensions }
+    }
+
+    fn inside_map(&self, pos: &Position) -> bool {
+        pos.x >= 0 && pos.y >= 0 && pos.x < self.dimensions.x && pos.y < self.dimensions.y
+    }
+
+    fn count_antinodes(&self) -> usize {
+        let mut antinodes = HashSet::new();
+
+        for (pos1, antenna) in &self.antennas {
+            for (pos2, _) in self.antennas.iter().filter(|&(_, a)| a == antenna).filter(|&(p, _)| p != pos1) {
+                let antinode_pos = pos1.add_position(pos2);
+                if self.inside_map(&antinode_pos) {
+                    antinodes.insert(antinode_pos);
+                }
+            }
+        }
+
+        antinodes.len()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let input = [
+            "............",
+            "........0...",
+            ".....0......",
+            ".......0....",
+            "....0.......",
+            "......A.....",
+            "............",
+            "............",
+            "........A...",
+            ".........A..",
+            "............",
+            "............",
+        ].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
+        assert_eq!(Map::new(&input).count_antinodes(), 14);
+    }
+}