1 files changed, 136 insertions, 0 deletions

diff --git a/day5/src/main.rs b/day5/src/main.rs
new file mode 100644
index 0000000..e55b244
--- /dev/null
+++ b/day5/src/main.rs
@@ -0,0 +1,136 @@
+use std::fs;
+use std::path::Path;
+use regex::Regex;
+use lazy_static::lazy_static;
+
+#[derive(Debug,PartialEq)]
+struct Segment(u32,u32,u32,u32);
+
+impl Segment {
+    fn is_hor(&self) -> bool {
+        self.1 == self.3
+    }
+    fn is_ver(&self) -> bool {
+        self.0 == self.2
+    }
+}
+
+/* AOC21 Day 7: https://adventofcode.com/2021/day/7 */
+fn main() {
+    let input = Path::new("resources").join("input.txt");
+    let content = fs::read_to_string(input).expect("Unable to read input file");
+    let (size, segments) = parse_input(&content);
+    let area = radar(&segments, size, false);
+    println!("Ex1: The result is: {}", area.iter().filter(|&&c| c > 1).count());
+    let area = radar(&segments, size, true);
+    println!("Ex2: The result is: {}", area.iter().filter(|&&c| c > 1).count());
+}
+
+fn radar(segments: &[Segment], size: u32, diagonals: bool) -> Vec<u32> {
+    let mut area = vec![0;(size+1).pow(2) as usize];
+    segments.iter().for_each(
+        |s| match s {
+            s if s.is_hor() => { 
+                range(s.0, s.2).iter().for_each(|x| area[((size+1)*s.1 + x) as usize] += 1)
+            },
+            s if s.is_ver() => { 
+                range(s.1, s.3).iter().for_each(|y| area[((size+1)*y + s.0) as usize] += 1)
+            },
+            s => {
+                if diagonals {
+                    range(s.0,s.2).iter().zip(range(s.1,s.3)).for_each(|(x,y)| area[((size+1)*y + x) as usize] += 1)
+                }
+            }
+        }
+    );
+    area
+}
+
+fn parse_input(s: &str) -> (u32, Vec<Segment>) {
+    lazy_static! {
+        static ref RE: Regex = Regex::new(r"^(\d+),(\d+) -> (\d+),(\d+)$").unwrap();
+    }
+    let mut max = 0;
+    let segs = s.lines().map(|l| {
+        let caps = RE.captures(l).expect("Malformed input");
+        let x1 = caps.get(1).unwrap().as_str().parse().expect("Malformed input");
+        let y1 = caps.get(2).unwrap().as_str().parse().expect("Malformed input");
+        let x2 = caps.get(3).unwrap().as_str().parse().expect("Malformed input");
+        let y2 = caps.get(4).unwrap().as_str().parse().expect("Malformed input");
+        max = *[x1, x2, y1, y2, max].iter().max().unwrap();
+        Segment(x1, y1, x2, y2)
+    }).collect();
+    (max, segs)
+}
+
+fn range(from: u32, to: u32) -> Vec<u32> {
+    if from < to {
+        (from..=to).collect()
+    } else {
+        (to..=from).rev().collect()
+    }
+} 
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const INPUT: &str = "0,9 -> 5,9
+8,0 -> 0,8
+9,4 -> 3,4
+2,2 -> 2,1
+7,0 -> 7,4
+6,4 -> 2,0
+0,9 -> 2,9
+3,4 -> 1,4
+0,0 -> 8,8
+5,5 -> 8,2";
+
+    #[test]
+    fn input_parsing() {
+        let (size, segments) = parse_input(INPUT);
+        assert_eq!(9,size);
+        assert_eq!(vec![
+            Segment(0,9,5,9),
+            Segment(8,0,0,8),
+            Segment(9,4,3,4),
+            Segment(2,2,2,1),
+            Segment(7,0,7,4),
+            Segment(6,4,2,0),
+            Segment(0,9,2,9),
+            Segment(3,4,1,4),
+            Segment(0,0,8,8),
+            Segment(5,5,8,2),
+        ],segments);
+    }
+
+    #[test]
+    fn examples() {
+        let (size, segments) = parse_input(INPUT);
+        assert_eq!(vec![
+            0,0,0,0,0,0,0,1,0,0,
+            0,0,1,0,0,0,0,1,0,0,
+            0,0,1,0,0,0,0,1,0,0,
+            0,0,0,0,0,0,0,1,0,0,
+            0,1,1,2,1,1,1,2,1,1,
+            0,0,0,0,0,0,0,0,0,0,
+            0,0,0,0,0,0,0,0,0,0,
+            0,0,0,0,0,0,0,0,0,0,
+            0,0,0,0,0,0,0,0,0,0,
+            2,2,2,1,1,1,0,0,0,0
+        ], radar(&segments, size, false));
+        assert_eq!(vec![
+            1,0,1,0,0,0,0,1,1,0,
+            0,1,1,1,0,0,0,2,0,0,
+            0,0,2,0,1,0,1,1,1,0,
+            0,0,0,1,0,2,0,2,0,0,
+            0,1,1,2,3,1,3,2,1,1,
+            0,0,0,1,0,2,0,0,0,0,
+            0,0,1,0,0,0,1,0,0,0,
+            0,1,0,0,0,0,0,1,0,0,
+            1,0,0,0,0,0,0,0,1,0,
+            2,2,2,1,1,1,0,0,0,0
+        ], radar(&segments, size, true))
+    }
+
+}