Use address halos to calculate part halos

2023/src/day3.rs

@@ -22,6 +22,32 @@ struct Addr {
     col: usize,
 }
 
+impl Addr {
+    fn halo(&self) -> impl Iterator<Item = Addr> {
+        let row = self.row as i32;
+        let col = self.col as i32;
+        vec![
+            (row - 1, col - 1),
+            (row, col - 1),
+            (row + 1, col - 1),
+            //
+            (row - 1, col),
+            (row, col),
+            (row + 1, col),
+            //
+            (row - 1, col + 1),
+            (row, col + 1),
+            (row + 1, col + 1),
+        ]
+        .into_iter()
+        .filter(|(row, col)| *row >= 0 && *col >= 0)
+        .map(|(row, col)| Addr {
+            row: row as usize,
+            col: col as usize,
+        })
+    }
+}
+
 #[derive(Clone, Debug, PartialEq)]
 struct Part {
     value: u32,
@@ -31,39 +57,38 @@ struct Part {
 }
 
 impl Part {
-    fn span(&self) -> Vec<Addr> {
-        (self.start..self.end + 1)
-            .map(|addr| Addr {
+    fn span<'a>(&'a self) -> impl Iterator<Item = Addr> + 'a {
+        (self.start..self.end + 1).map(|addr| Addr {
             row: self.row,
             col: addr,
         })
-            .collect()
     }
 
-    fn halo(&self, max_row: usize, max_col: usize) -> Vec<Addr> {
-        let mut halo: Vec<(i32, i32)> = vec![];
-
-        for r in self.start..self.end + 1 {
-            halo.push((self.row as i32 - 1, r as i32));
-            halo.push((self.row as i32 + 1, r as i32));
-        }
-
-        halo.push((self.row as i32 - 1, self.start as i32 - 1));
-        halo.push((self.row as i32, self.start as i32 - 1));
-        halo.push((self.row as i32 + 1, self.start as i32 - 1));
-        halo.push((self.row as i32 - 1, self.end as i32 + 1));
-        halo.push((self.row as i32, self.end as i32 + 1));
-        halo.push((self.row as i32 + 1, self.end as i32 + 1));
-
-        halo.into_iter()
-            .filter(|(row, col)| {
-                *row >= 0 && *row <= max_row as i32 && *col >= 0 && *col <= max_col as i32
+    fn halo<'a>(&'a self, max_row: usize, max_col: usize) -> impl IntoIterator<Item = Addr> {
+        println!("{:?}", self);
+        let addresses = self
+            .span()
+            .map(|addr| addr.halo())
+            .flatten()
+            .filter(|Addr { row, col }| {
+                *row as i32 >= 0
+                    && *row as i32 <= max_row as i32
+                    && *col as i32 >= 0
+                    && *col as i32 <= max_col as i32
             })
-            .map(|(row, col)| Addr {
-                row: row as usize,
-                col: col as usize,
-            })
-            .collect()
+            .fold(HashSet::new(), |mut acc, val| {
+                let _ = acc.insert(val);
+                acc
+            });
+
+        println!("{:?}", addresses);
+        println!("{:?}", self.span().collect::<HashSet<Addr>>());
+        println!("{:?}", addresses.difference(&self.span().collect()));
+
+        addresses
+            .difference(&self.span().collect())
+            .map(|addr| addr.clone())
+            .collect::<HashSet<Addr>>()
     }
 }
 
@@ -112,8 +137,10 @@ fn find_gears(schematic: String) -> Vec<Gear> {
                 end: addr.col,
             }
             .halo(max_row - 1, max_col - 1)
+            .into_iter()
+            .collect::<HashSet<Addr>>()
         })
-        .collect::<Vec<Vec<Addr>>>();
+        .collect::<Vec<HashSet<Addr>>>();
 
     let mut gears = vec![];
     for splat in splats {
@@ -130,7 +157,7 @@ fn find_gears(schematic: String) -> Vec<Gear> {
     gears
 }
 
-fn part_within_halo(halo1: Vec<Addr>, part: Part) -> bool {
+fn part_within_halo(halo1: impl IntoIterator<Item = Addr>, part: Part) -> bool {
     let halo1: HashSet<Addr> = halo1.into_iter().collect::<HashSet<Addr>>();
     let halo2: HashSet<Addr> = part.span().into_iter().collect::<HashSet<Addr>>();
 
@@ -352,7 +379,9 @@ mod test {
             end: 2,
         };
         assert_eq!(
-            part.halo(schematic.len() - 1, schematic[0].len() - 1),
+            part.halo(schematic.len() - 1, schematic[0].len() - 1)
+                .into_iter()
+                .collect::<HashSet<Addr>>(),
             vec![
                 Addr { row: 1, col: 0 },
                 Addr { row: 1, col: 1 },
@@ -360,6 +389,8 @@ mod test {
                 Addr { row: 0, col: 3 },
                 Addr { row: 1, col: 3 }
             ]
+            .into_iter()
+            .collect::<HashSet<Addr>>()
         );
 
         assert_eq!(
@@ -369,7 +400,9 @@ mod test {
                 start: 1,
                 end: 1
             }
-            .halo(schematic.len() - 1, schematic[0].len() - 1),
+            .halo(schematic.len() - 1, schematic[0].len() - 1)
+            .into_iter()
+            .collect::<HashSet<Addr>>(),
             vec![
                 Addr { row: 0, col: 1 },
                 Addr { row: 2, col: 1 },
@@ -380,6 +413,8 @@ mod test {
                 Addr { row: 1, col: 2 },
                 Addr { row: 2, col: 2 }
             ]
+            .into_iter()
+            .collect::<HashSet<Addr>>()
         );
         assert_eq!(
             Part {
@@ -388,7 +423,9 @@ mod test {
                 start: 2,
                 end: 4,
             }
-            .halo(schematic.len() - 1, schematic[0].len() - 1),
+            .halo(schematic.len() - 1, schematic[0].len() - 1)
+            .into_iter()
+            .collect::<HashSet<Addr>>(),
             vec![
                 Addr { row: 5, col: 2 },
                 Addr { row: 7, col: 2 },
@@ -403,6 +440,8 @@ mod test {
                 Addr { row: 6, col: 5 },
                 Addr { row: 7, col: 5 },
             ]
+            .into_iter()
+            .collect::<HashSet<Addr>>()
         );
     }