day(09): refactor

• Implement ‹new› for ‹Instruction›
• Pass ‹visited› instead of returning and consuming

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

src/bin/day09.rs

@@ -45,6 +45,13 @@ struct Instruction {
     steps: i32,
 }
 
+impl Instruction {
+    #[cfg(test)]
+    fn new(direction: Direction, steps: i32) -> Self {
+        Self { direction, steps }
+    }
+}
+
 impl FromStr for Instruction {
     type Err = Report;
 
@@ -98,16 +105,14 @@ impl State {
         State { knots }
     }
 
-    fn execute(&self, i: &Instruction) -> (BTreeSet<Position>, State) {
-        let mut visited = BTreeSet::new();
-
+    fn execute(&self, visited: &mut BTreeSet<Position>, i: &Instruction) -> State {
         // debug!("\n{}", self.show(6, 5));
         let mut state: State = self.clone();
         for _ in 0..i.steps {
-            state = state.execute_step(&mut visited, &i.direction);
+            state = state.execute_step(visited, &i.direction);
         }
 
-        (visited, state)
+        state
     }
 
     // fn show(&self, width: i32, height: i32) -> String {
@@ -136,10 +141,7 @@ fn execute(knots: i32, input: &Input) -> Output {
     let mut visited = BTreeSet::<Position>::new();
 
     input.iter().fold(State::new(knots), |state, instruction| {
-        let (mut v, s) = state.execute(instruction);
-        visited.append(&mut v);
-
-        s
+        state.execute(&mut visited, instruction)
     });
 
     visited.len()
@@ -173,38 +175,14 @@ mod day_09_extended {
     #[test]
     fn test_part_2_bigger_sample() {
         let input = vec![
-            Instruction {
-                direction: Direction::Right,
-                steps: 5,
-            },
-            Instruction {
-                direction: Direction::Up,
-                steps: 8,
-            },
-            Instruction {
-                direction: Direction::Left,
-                steps: 8,
-            },
-            Instruction {
-                direction: Direction::Down,
-                steps: 3,
-            },
-            Instruction {
-                direction: Direction::Right,
-                steps: 17,
-            },
-            Instruction {
-                direction: Direction::Down,
-                steps: 10,
-            },
-            Instruction {
-                direction: Direction::Left,
-                steps: 25,
-            },
-            Instruction {
-                direction: Direction::Up,
-                steps: 20,
-            },
+            Instruction::new(Direction::Right, 5),
+            Instruction::new(Direction::Up, 8),
+            Instruction::new(Direction::Left, 8),
+            Instruction::new(Direction::Down, 3),
+            Instruction::new(Direction::Right, 17),
+            Instruction::new(Direction::Down, 10),
+            Instruction::new(Direction::Left, 25),
+            Instruction::new(Direction::Up, 20),
         ];
 
         assert_eq!(Day09::part_2(&input), 36);