day14 solution 1

1 files changed, 100 insertions, 0 deletions

diff --git a/src/bin/day14.rs b/src/bin/day14.rs
new file mode 100644
index 0000000..531e1b4
--- /dev/null
+++ b/src/bin/day14.rs
@@ -0,0 +1,100 @@
+use regex::Regex;
+use std::collections::HashMap;
+
+static DAY: u8 = 14;
+
+fn main() {
+    let input = advent::read_lines(DAY);
+    println!("{DAY}a: {}", safety_factor(&input, Position { x: 101, y: 103 }));
+    println!("{DAY}b: {}", 0);
+}
+
+struct Position {
+    x: isize,
+    y: isize,
+}
+
+struct Robot {
+    pos: Position,
+    velocity: Position,
+}
+
+impl Robot {
+    fn new(input: &str) -> Robot {
+        let re = Regex::new(r"p=([0-9]+),([0-9]+) v=([-0-9]+),([-0-9]+)").unwrap();
+        let caps = re.captures(input).unwrap();
+        let x = caps.get(1).unwrap().as_str().parse::<isize>().unwrap();
+        let y = caps.get(2).unwrap().as_str().parse::<isize>().unwrap();
+        let dx = caps.get(3).unwrap().as_str().parse::<isize>().unwrap();
+        let dy = caps.get(4).unwrap().as_str().parse::<isize>().unwrap();
+
+        Robot {
+            pos: Position { x, y },
+            velocity: Position { x: dx, y: dy },
+        }
+    }
+
+    fn travel(&mut self, area: &Position) {
+        self.pos.x = (self.pos.x + self.velocity.x + area.x) % area.x;
+        self.pos.y = (self.pos.y + self.velocity.y + area.y) % area.y;
+    }
+
+    fn quadrant(&self, area: &Position) -> u8 {
+        if self.pos.x < area.x / 2 && self.pos.y < area.y / 2 {
+            1
+        } else if self.pos.x < area.x / 2 && self.pos.y > area.y / 2 {
+            2
+        } else if self.pos.x > area.x / 2 && self.pos.y < area.y / 2 {
+            3
+        } else if self.pos.x > area.x / 2 && self.pos.y > area.y / 2 {
+            4
+        } else {
+            0
+        }
+    }
+}
+
+fn safety_factor(input: &[String], area: Position) -> u32 {
+    let mut robots = input.iter()
+                           .map(|line| Robot::new(line))
+                           .collect::<Vec<_>>();
+    for _ in 0 .. 100 {
+        for robot in robots.iter_mut() {
+            robot.travel(&area);
+        }
+    }
+
+    let mut quadrants = HashMap::new();
+    for robot in &robots {
+        let quadrant = robot.quadrant(&area);
+        if quadrant != 0 {
+            let entry = quadrants.entry(quadrant).or_insert(0);
+            *entry += 1;
+        }
+    }
+    quadrants.values().product()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let input = [
+            "p=0,4 v=3,-3",
+            "p=6,3 v=-1,-3",
+            "p=10,3 v=-1,2",
+            "p=2,0 v=2,-1",
+            "p=0,0 v=1,3",
+            "p=3,0 v=-2,-2",
+            "p=7,6 v=-1,-3",
+            "p=3,0 v=-1,-2",
+            "p=9,3 v=2,3",
+            "p=7,3 v=-1,2",
+            "p=2,4 v=2,-3",
+            "p=9,5 v=-3,-3",
+        ].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
+        assert_eq!(safety_factor(&input, Position { x: 11, y: 7}), 12);
+    }
+}