From 05704d9ba10e0abfa106adf3e07d9a73b89cc7ef Mon Sep 17 00:00:00 2001
From: Malte Tammena <malte.tammena@pm.me>
Date: Fri, 9 Dec 2022 21:41:23 +0100
Subject: [PATCH] Try some optimization

---
 day03/src/bitmask.rs | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/day03/src/bitmask.rs b/day03/src/bitmask.rs
index 31028fd..fa91535 100644
--- a/day03/src/bitmask.rs
+++ b/day03/src/bitmask.rs
@@ -10,15 +10,16 @@ impl Bitmask {
     }
     pub const fn from_alpha(alpha: &u8) -> Self {
         // 'a' is the LSB, 'Z' is MSB
-        if *alpha <= b'Z' {
-            Self(1 << (alpha - b'A' + 26))
-        } else {
-            Self(1 << (alpha - b'a'))
-        }
+        Self(1 << (alpha - b'A'))
     }
     /// Get the priority from a rucksack entry
     pub const fn to_priority(self) -> super::Prio {
-        self.0.trailing_zeros() as usize + 1
+        let log = self.0.trailing_zeros() as u8;
+        if log < 32 {
+            log as usize + 27
+        } else {
+            log as usize - 31
+        }
     }
 }
 
@@ -50,13 +51,21 @@ mod tests {
 
     #[test]
     fn bitmask_works() {
+        assert_eq!(Bitmask::from_alpha(&b'A'), Bitmask(1));
+        assert_eq!(Bitmask::from_alpha(&b'Z'), Bitmask(1 << 25));
+        assert_eq!(Bitmask::from_alpha(&b'a'), Bitmask(1 << 32));
+        assert_eq!(Bitmask::from_alpha(&b'z'), Bitmask(1 << 57));
         assert_eq!(
             crate::parse_chars::<String>("abc".into()),
-            Bitmask::from_raw(7)
+            Bitmask((1 << 32) + (1 << 33) + (1 << 34))
         );
         assert_eq!(
             crate::parse_chars::<String>("Z".into()),
-            Bitmask::from_raw(1 << 51)
+            Bitmask::from_raw(1 << 25)
         );
+        assert_eq!(Bitmask::from_alpha(&b'a').to_priority(), 1);
+        assert_eq!(Bitmask::from_alpha(&b'z').to_priority(), 26);
+        assert_eq!(Bitmask::from_alpha(&b'A').to_priority(), 27);
+        assert_eq!(Bitmask::from_alpha(&b'Z').to_priority(), 52);
     }
 }