2017/13

2017/13/src/main.rs

@@ -0,0 +1,67 @@
+use std::io::{self, BufRead};
+
+#[derive(Debug)]
+struct Layer {
+    depth: usize,
+    range: usize,
+}
+
+impl Layer {
+    fn new(depth: usize, range: usize) -> Layer {
+        Layer { depth, range }
+    }
+
+    fn is_scanner_at(&self, delta: usize, index: usize) -> bool {
+        let time = self.depth + delta;
+        let c = (self.range - 1) * 2;
+
+        time % c == index || time % c == (c - index)
+    }
+
+    fn severity(&self) -> usize {
+        self.depth * self.range
+    }
+}
+
+fn main() {
+    let stdin = io::stdin();
+
+    let firewall = stdin
+        .lock()
+        .lines()
+        .filter_map(Result::ok)
+        .map(|line| {
+            let digits = line
+                .split(": ")
+                .map(|digit| digit.parse::<usize>().expect("failed to parse digit"))
+                .collect::<Vec<_>>();
+
+            Layer::new(digits[0], digits[1])
+        }).collect::<Vec<_>>();
+
+    let mut severity = 0;
+
+    for layer in &firewall {
+        if layer.is_scanner_at(0, 0) {
+            severity += layer.severity();
+        }
+    }
+
+    println!("part.one={}", severity);
+
+    let mut delta = 0;
+
+    'iteration: loop {
+        for layer in &firewall {
+            if layer.is_scanner_at(delta, 0) {
+                delta += 1;
+
+                continue 'iteration;
+            }
+        }
+
+        break;
+    }
+
+    println!("part.two={}", delta);
+}