Day 4, Part 1 & 2

src/bin/d4.rs

@@ -0,0 +1,44 @@
+const INPUT: &str = include_str!("../input/d4.txt");
+
+fn main() -> anyhow::Result<()> {
+    let p1 = INPUT
+        .split('\n')
+        .map(Pair::from)
+        .filter(ranges_contain_each_other)
+        .count();
+    println!("{p1}");
+    let p2 = INPUT
+        .split('\n')
+        .map(Pair::from)
+        .filter(ranges_overlap)
+        .count();
+    println!("{p2}");
+    anyhow::Ok(())
+}
+
+struct Pair(usize, usize, usize, usize);
+
+impl From<&str> for Pair {
+    fn from(line: &str) -> Self {
+        let v = line
+            .split(['-', ','])
+            .map(|s| {
+                s.parse::<usize>()
+                    .expect("Failed to parse section ID as usize")
+            })
+            .collect::<Vec<_>>();
+        assert_eq!(v.len(), 4, "Expected 4 section IDs, line: {line}");
+        Pair(v[0], v[1], v[2], v[3])
+    }
+}
+
+fn ranges_contain_each_other(pair: &Pair) -> bool {
+    ((pair.0 <= pair.2)
+        && (pair.3 <= pair.1))
+    || ((pair.2 <= pair.0)
+        && (pair.1 <= pair.3))
+}
+
+fn ranges_overlap(pair: &Pair) -> bool {
+    !((pair.1 < pair.2) || (pair.3 < pair.0))
+}