add day 8, part 2

day08/part2.rs

@@ -0,0 +1,58 @@
+// Copyright 2022 Christian Ulrich
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+// usage: ./part2 < input
+
+pub mod common;
+
+use common::Forest;
+
+fn main() -> Result<(), &'static str> {
+    let forest = Forest::from_stdin()?;
+    let (x_len, y_len) = forest.dimensions();
+    let mut result = 0;
+    for y in 0..y_len {
+        for x in 0..x_len {
+            let line = forest.line(y).unwrap().collect::<Vec<_>>();
+            let column = forest.column(x).unwrap().collect::<Vec<_>>();
+
+            let west = Box::new(line[..x].iter().rev().cloned());
+            let east = Box::new(line[x + 1..].iter().cloned());
+            let north = Box::new(column[..y].iter().rev().cloned());
+            let south = Box::new(column[y + 1..].iter().cloned());
+            let views: [Box<dyn Iterator<Item = _>>; 4] = [west, east, north, south];
+
+            let tree = forest.tree(x, y).unwrap();
+            let mut scenic_score = 1;
+            for view in views {
+                let mut viewing_distance = 0;
+                for t in view {
+                    match t {
+                        _ if { t >= &tree } => {
+                            viewing_distance += 1;
+                            break;
+                        }
+                        _ if { t < &tree } => viewing_distance += 1,
+                        _ => break,
+                    }
+                }
+                scenic_score *= viewing_distance;
+            }
+            result = usize::max(result, scenic_score);
+        }
+    }
+    println!("{result}");
+    Ok(())
+}