solution: day 8

src/days.rs

@@ -5,7 +5,7 @@ pub mod d4;
 pub mod d5;
 pub mod d6;
 pub mod d7;
-// pub mod d8;
+pub mod d8;
 // pub mod d9;
 // pub mod d10;
 // pub mod d11;

src/days/d8.rs

@@ -0,0 +1,91 @@
+use crate::prelude::*;
+
+pub type I = (M<char, Vec<(isize, isize)>>, isize, isize);
+pub type O = usize;
+
+fn _parse (data: &str) -> I {
+    let data = data.trim();
+    let lines = data.lines();
+
+    let mut w = 0;
+    let mut h = 0;
+
+    let mut m: M<char, Vec<(isize, isize)>> = M::new();
+
+    for l in lines {
+        let l = l.trim();
+        w = l.len();
+        for (i, c) in l.chars().enumerate() {
+            m.entry(c).or_default().push((h as isize, i as isize));
+        }
+        h += 1;
+    }
+
+    m.remove(&'.');
+
+    (m, w as isize, h as isize)
+}
+
+fn _solve ((map, width, height): I, n: isize) -> O {
+    let is_valid = |(y, x): &(isize, isize)| (0..width).contains(x) && (0..height).contains(y);
+
+    let mut s = S::new();
+
+    for v in map.values() {
+        for (a, b) in v.into_iter().tuple_combinations() {
+            let ydiff = b.0 - a.0;
+            let xdiff = b.1 - a.1;
+
+            if n > 1 {
+                s.insert(*a);
+                s.insert(*b);
+            }
+
+            for i in 1..=n {
+                let ydiff_mul = ydiff * i;
+                let xdiff_mul = xdiff * i;
+
+                let new = [(b.0 + ydiff_mul, b.1 + xdiff_mul), (a.0 - ydiff_mul, a.1 - xdiff_mul)];
+
+                s.extend(new.into_iter().filter(is_valid));
+
+            }
+        }
+    };
+
+    s.len()
+}
+
+fn _silver (i: I) -> O {
+    _solve(i, 1)
+}
+
+fn _gold (i: I) -> O {
+    _solve(i, 50)
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    fn read () -> I {
+        let data = inc!(8);
+        _parse(data)
+    }
+
+    #[test]
+    fn silver () {
+        let data = read();
+        let ans = _silver(data);
+
+        assert_eq!(ans, 299)
+    }
+
+    #[test]
+    fn gold () {
+        let data = read();
+        let ans = _gold(data);
+
+        assert_eq!(ans, 1032)
+    }
+}