[TASK] Solved day 3

src/day3.rs

@@ -0,0 +1,52 @@
+use super::util;
+
+pub fn solve() {
+    let lines = util::read_file("input/day3.txt");
+    let forest = Forest {
+        map: lines.iter().flat_map(|l| l.chars().map(|c| c == '#')).collect(),
+        width: lines.iter().next().unwrap().len(),
+        height: lines.len()
+    };
+
+    let angle = Angle { x: 3, y: 1 };
+    println!("Day 3 Part 1: {}", forest.trees_on_angle(&angle));
+
+    let angles = [ Angle {x: 1, y: 1}, Angle {x: 3, y: 1}, Angle {x: 5, y: 1}, Angle {x: 7, y: 1}, Angle{x: 1, y: 2}];
+    let part2 = angles.iter().map(|a| forest.trees_on_angle(a)).fold(1, |res, cur| res * cur);
+
+    println!("Day 3 Part 2: {}", part2);
+}
+
+struct Forest {
+    map: Vec<bool>,
+    width: usize,
+    height: usize,
+}
+
+struct Angle {
+    x: usize,
+    y: usize
+}
+
+impl Forest {
+
+    fn is_tree(&self, x: usize, y: usize) -> bool {
+
+        if y >= self.height {
+            panic!("Invalid coordinate!");
+        }
+
+        return self.map[(x % self.width) + y * self.width];
+    }
+
+    fn trees_on_angle(&self, angle: &Angle) -> u32 {
+        let mut res = 0;
+        for i in 0..(self.height / angle.y) {
+
+            if self.is_tree(angle.x * i, angle.y * i) {
+                res += 1;
+            }
+        }
+        return res;
+    }
+}

src/main.rs

@@ -4,6 +4,7 @@ use std::time::Instant;
 mod util;
 mod day1;
 mod day2;
+mod day3;
 
 fn main() {
 
@@ -16,12 +17,14 @@ fn main() {
         match args[day_arg_idx.unwrap() + 1].parse::<u8>().unwrap() {
             1 => day1::solve(),
             2 => day2::solve(),
+            3 => day3::solve(),
             _ => println!("This day is not yet implemented")
         }
     } else {
         // Solve all days:
         day1::solve();
         day2::solve();
+        day3::solve();
     }
 
     println!("Execution took {} μs", now.elapsed().as_micros());