Implementation day 10

2020/src/day10.rs

@@ -0,0 +1,71 @@
+use std::io::Read;
+
+use crate::common::from_lines;
+use crate::Solution;
+
+#[derive(Default)]
+pub struct Day10;
+
+impl Solution for Day10 {
+    fn part1(&mut self, input: &mut dyn Read) -> String {
+        let mut adapters: Vec<u32> = from_lines(input);
+        // Outlet
+        adapters.push(0);
+        adapters.sort();
+        let device = *adapters.last().unwrap() + 3;
+        adapters.push(device);
+
+        let mut differences = [0u32; 4];
+
+        for window in adapters.windows(2) {
+            differences[(window[1] - window[0]) as usize] += 1;
+        }
+
+        (differences[1] * differences[3]).to_string()
+    }
+
+    fn part2(&mut self, input: &mut dyn Read) -> String {
+        let mut adapters: Vec<u32> = from_lines(input);
+        adapters.push(0);
+        adapters.sort();
+
+        let mut methods = vec![0u64; adapters.len()];
+        methods[0] = 1;
+
+        for (i, a) in adapters.iter().copied().enumerate() {
+            let c = methods[i];
+
+            for (j, b) in adapters[i..].iter().enumerate().skip(1) {
+                if b - a <= 3 {
+                    methods[i + j] += c;
+                } else {
+                    break;
+                }
+            }
+        }
+
+        methods.last().unwrap().to_string()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::test_implementation;
+
+    use super::*;
+
+    const SAMPLE: &[u8] = include_bytes!("../samples/10.txt");
+    const SAMPLE2: &[u8] = include_bytes!("../samples/10.2.txt");
+
+    #[test]
+    fn sample_part1() {
+        test_implementation!(Day10, 1, SAMPLE, 35);
+        test_implementation!(Day10, 1, SAMPLE2, 220);
+    }
+
+    #[test]
+    fn sample_part2() {
+        test_implementation!(Day10, 2, SAMPLE, 8);
+        test_implementation!(Day10, 2, SAMPLE2, 19208);
+    }
+}

2020/src/lib.rs

@@ -10,6 +10,7 @@ mod day06;
 mod day07;
 mod day08;
 mod day09;
+mod day10;
 
 pub trait Solution {
     fn part1(&mut self, input: &mut dyn Read) -> String;
@@ -30,6 +31,7 @@ pub fn get_implementation(day: usize) -> Box<dyn Solution> {
         7 => Box::new(day07::Day07::default()),
         8 => Box::new(day08::Day08::default()),
         9 => Box::new(day09::Day09::default()),
+        10 => Box::new(day10::Day10::default()),
         _ => panic!("Unsupported day {}", day),
     }
 }