refactor 200 iterator

src/euler200/src/main.rs

@@ -13,7 +13,7 @@ fn main() {
     squbes.iterate();
     squbes.iterate();
     squbes.iterate();
-    println!("{:?}", squbes.output());
+    println!("{:?}", squbes.get_output());
 }
 
 #[derive(Debug)]
@@ -43,9 +43,14 @@ impl Squbes {
         self.calculate_squbes_with_current_prime();
         self.save_current_prime();
         self.update_current_prime();
+        self.save_new_squbes();
     }
 
-    pub fn output(&self) -> Vec<u64> {
+    fn save_new_squbes(&mut self) {
+        self.squbes.extend(self.new_squbes.drain(0..));
+    }
+
+    pub fn get_output(&self) -> Vec<u64> {
         let mut result: Vec<_> = self.squbes.iter().copied().collect();
         result.sort_unstable();
         result
@@ -60,18 +65,7 @@ impl Squbes {
     }
 
     fn calculate_squbes_with_current_prime(&mut self) {
-        assert_ne!(self.current_prime, 0);
-        let iter = self
-            .used_primes
-            .iter()
-            .copied()
-            .zip([self.current_prime].into_iter().cycle())
-            .chain(
-                [self.current_prime]
-                    .into_iter()
-                    .cycle()
-                    .zip(self.used_primes.iter().copied()),
-            )
+        let iter = get_iterator_over_pairs_both_ways(&self.used_primes, self.current_prime)
             .map(|(p, q)| Self::core(p, q));
         self.new_squbes.extend(iter);
     }
@@ -80,3 +74,14 @@ impl Squbes {
         p.pow(2) * q.pow(3)
     }
 }
+
+fn get_iterator_over_pairs_both_ways(
+    vec: &[u64],
+    value: u64,
+) -> impl Iterator<Item = (u64, u64)> + '_ {
+    iterate_vec_and_scalar(vec, value).flat_map(|(x, y)| [(x, y), (y, x)].into_iter())
+}
+
+fn iterate_vec_and_scalar(vec: &[u64], value: u64) -> impl Iterator<Item = (u64, u64)> + '_ {
+    vec.iter().copied().zip([value].into_iter().cycle())
+}