Day 13+formatting

.gitignore

@@ -1,3 +1,4 @@
 /target
 .history
 input
+src/template.rs

src/day12.rs

@@ -5,7 +5,7 @@ pub enum Direction {
     North,
     East,
     South,
-    West
+    West,
 }
 
 impl Direction {
@@ -15,7 +15,7 @@ impl Direction {
             1 => Self::South,
             2 => Self::West,
             3 => Self::North,
-            _ => unreachable!()
+            _ => unreachable!(),
         }
     }
 }
@@ -25,14 +25,14 @@ pub enum Command {
     Direction(Direction, i64),
     Left(i64),
     Right(i64),
-    Forward(i64)
+    Forward(i64),
 }
 
 #[derive(Debug)]
 pub struct Ship {
     rot: i64,
     pos: (i64, i64),
-    wp: (i64,i64)
+    wp: (i64, i64),
 }
 
 impl Ship {
@@ -40,7 +40,7 @@ impl Ship {
         Self {
             rot: 0,
             pos: (0, 0),
-            wp: (10,1)
+            wp: (10, 1),
         }
     }
 
@@ -68,9 +68,7 @@ impl Ship {
             Command::Right(n) => {
                 self.rot += n;
             }
-            Command::Forward(n) => {
-                self.cmd_p1(&Command::Direction(self.facing(),*n))
-            }
+            Command::Forward(n) => self.cmd_p1(&Command::Direction(self.facing(), *n)),
         }
     }
 
@@ -95,7 +93,7 @@ impl Ship {
                     1 => (wp.1, -wp.0),
                     2 => (-wp.0, -wp.1),
                     3 => (-wp.1, wp.0),
-                    _ => unreachable!()
+                    _ => unreachable!(),
                 };
             }
             Command::Left(n) => {
@@ -105,7 +103,7 @@ impl Ship {
                     1 => (-wp.1, wp.0),
                     2 => (-wp.0, -wp.1),
                     3 => (wp.1, -wp.0),
-                    _ => unreachable!()
+                    _ => unreachable!(),
                 };
             }
             Command::Forward(n) => {
@@ -132,9 +130,10 @@ pub fn input_generator(input: &str) -> Vec<Command> {
                 'L' if num % 90 == 0 => Command::Left((num / 90) % 4),
                 'R' if num % 90 == 0 => Command::Right((num / 90) % 4),
                 'F' => Command::Forward(num),
-                _ => panic!("Invalid command: {}",l)
+                _ => panic!("Invalid command: {}", l),
             }
-        }).collect::<Vec<Command>>()
+        })
+        .collect::<Vec<Command>>()
 }
 
 #[aoc(day12, part1)]

src/day13.rs

@@ -0,0 +1,74 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+
+#[derive(Debug)]
+pub struct BusInfo {
+    earliest: u64,
+    busses: Vec<u64>,
+}
+
+type Data = BusInfo;
+
+#[aoc_generator(day13)]
+pub fn input_generator(input: &str) -> Data {
+    let mut l = input.lines();
+    let earliest = l.next().unwrap().parse().unwrap();
+    let busses = l
+        .next()
+        .unwrap()
+        .split(',')
+        .map(|c| match c {
+            "x" => 0,
+            n => n.parse().unwrap(),
+        })
+        .collect();
+    BusInfo { earliest, busses }
+}
+
+#[aoc(day13, part1)]
+pub fn solve_part1(input: &Data) -> usize {
+    let e = input.earliest;
+    let mut min = std::u64::MAX;
+    let mut min_id = 0;
+    for n in &input.busses {
+        if *n == 0 {
+            continue;
+        }
+        let m = n - (e % n);
+        if m < min {
+            min = m;
+            min_id = *n;
+        }
+    }
+    return min as usize * min_id as usize;
+}
+
+#[aoc(day13, part2)]
+pub fn solve_part2(input: &Data) -> i64 {
+    let b = input
+        .busses
+        .iter()
+        .enumerate()
+        .filter(|(_, n)| **n != 0)
+        .map(|(a, b)| (a as i64, *b as i64))
+        .collect::<Vec<_>>();
+    let mut t = 0;
+    let target = b.iter().map(|(_, b)| b).fold(1, |a, b| a * b);
+    loop {
+        let mut cnt = 0;
+        let dt = b
+            .iter()
+            .filter_map(|(i, n)| {
+                if (t + i) % n == 0 {
+                    cnt += 1;
+                    Some(*n)
+                } else {
+                    None
+                }
+            })
+            .fold(1, |a, b| a * b);
+        if dt == target {
+            return t % dt;
+        }
+        t += dt;
+    }
+}

src/lib.rs

@@ -11,4 +11,5 @@ pub mod day09;
 pub mod day10;
 pub mod day11;
 pub mod day12;
+pub mod day13;
 aoc_lib! { year = 2020 }