Optimize & simplify day 1

bram/rust/src/day_01/mod.rs

@@ -1,55 +1,41 @@
 use crate::utils;
 
-struct Dial {
-    points_at : i16,
-    clicks : u32,
-    passing_clicks : u32,
-}
-impl Dial {
-    fn new() -> Dial {
-        Dial { points_at : 50, clicks : 0, passing_clicks : 0 }
-    }
-
-    fn rotate_by(&mut self, r : i16) -> () {
-        let start : i16 = self.points_at;
-
-        self.points_at += r;
-        self.points_at = self.points_at.rem_euclid(100);
-        self.passing_clicks += (r.abs() / 100) as u32;
-
-        if self.points_at == 0 {
-            self.clicks += 1;
-
-            // Avoid double counting when starting and landing on zero
-            if r / 100 != 0 && r % 100 == 0 {
-                self.passing_clicks -= 1;
-            }
-        }
-
-        if r < 0 && start < self.points_at && start != 0 {
-            self.passing_clicks += 1;
-        }
-        if r > 0 && start > self.points_at && self.points_at != 0 {
-            self.passing_clicks += 1;
-        }
-
-        // println!(
-        //     "Dial {} now points at {} ({} clicks, {} passing)",
-        //     r, self.points_at, self.clicks, self.passing_clicks
-        // );
-    }
-}
-
-pub fn answer(text : String) ->( u32, u32 ) {
-    let mut dial : Dial = Dial::new();
+pub fn answer(text : String) ->( u16, u16 ) {
+    let mut old : i16 = 50;
+    let mut clicks : u16 = 0;
+    let mut passing_clicks : u16 = 0;
 
     for d in text.split("\n").filter_map(str_to_dir) {
-        dial.rotate_by(d);
+        let new : i16 = old + d;
+
+        // Part 1 clicks
+        if new % 100 == 0 {
+            clicks += 1;
+        }
+
+        // Part 2 clicks
+        if d > 0 {
+            passing_clicks += (
+                new.div_euclid(100) - old.div_euclid(100)
+            ) as u16
+        } else {
+            passing_clicks += (
+                (old - 1).div_euclid(100) - (new - 1).div_euclid(100)
+            ) as u16
+        }
+
+        old = new;
     }
 
-    ( dial.clicks
-    , dial.clicks + dial.passing_clicks
-    )
+    ( clicks, passing_clicks )
+}
+
+fn count_passing_clicks(old : i16, new : i16) -> u16 {
+    if old < new {
+        (new.div_euclid(100) - old.div_euclid(100)).abs() as u16
+    } else {
+        ((new - 1).div_euclid(100) - (old - 1).div_euclid(100)).abs() as u16
+    }
 }
 
 fn str_to_dir(s : &str) -> Option<i16> {