day(06): introduce a helper function for filtering

Signed-off-by: Matej Focko <mfocko@redhat.com>

src/bin/day06.rs

@@ -9,6 +9,12 @@ struct Race {
     distance: i64,
 }
 
+impl Race {
+    fn is_better(&self, t: i64) -> bool {
+        t * (self.time - t) > self.distance
+    }
+}
+
 struct Day06 {
     races: Vec<Race>,
 }
@@ -63,20 +69,14 @@ impl Solution<Output1, Output2> for Day06 {
     fn part_1(&mut self) -> Output1 {
         self.races
             .iter()
-            .map(|r| {
+            .map(|r| (1..r.time).filter(|t| r.is_better(*t)).count() as i32)
-                (1..r.time)
-                    .filter(|t| (r.time - t) * t > r.distance)
-                    .count() as i32
-            })
             .product()
     }
 
     fn part_2(&mut self) -> Output2 {
         let merged = self.merge_races();
 
-        (1..merged.time)
+        (1..merged.time).filter(|t| merged.is_better(*t)).count() as i32
-            .filter(|t| (merged.time - t) * t > merged.distance)
-            .count() as i32
     }
 }