day 5 part 1

src/day5.rs

@@ -0,0 +1,56 @@
+use aoc_runner_derive::aoc;
+
+use std::fmt;
+
+#[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd)]
+pub struct SeatId(u16);
+impl fmt::Display for SeatId {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        <Self as fmt::Debug>::fmt(self, f)
+    }
+}
+
+impl SeatId {
+    fn parse(input: &[u8]) -> Option<SeatId> {
+        if input.len() != 10 {
+            return None;
+        }
+        let mut seatid = 0u16;
+
+        for b in &input[..7] {
+            let value = match b {
+                b'F' => 0,
+                b'B' => 1,
+                _ => return None,
+            };
+            seatid = (seatid << 1) | value;
+        }
+
+        for b in &input[7..10] {
+            let value = match b {
+                b'L' => 0,
+                b'R' => 1,
+                _ => return None,
+            };
+            seatid = (seatid << 1) | value;
+        }
+        Some(SeatId(seatid))
+    }
+
+    fn row(&self) -> u8 {
+        (self.0 >> 3) as u8
+    }
+
+    fn column(&self) -> u8 {
+        (self.0 & 0b111) as u8
+    }
+}
+
+#[aoc(day5, part1)]
+pub fn solve_d5_p1(input: &[u8]) -> SeatId {
+    input
+        .split(|&b| b == b'\n')
+        .map(|i| SeatId::parse(i).unwrap())
+        .max()
+        .unwrap()
+}

src/lib.rs

@@ -2,5 +2,6 @@ pub mod day1;
 pub mod day2;
 pub mod day3;
 pub mod day4;
+pub mod day5;
 
 aoc_runner_derive::aoc_lib! { year = 2020 }