Day 8, puzzle 2

src/bin/d8p2.rs

@@ -0,0 +1,22 @@
+use aoc22::{
+    day8::{self, calc_scenic_score},
+    util,
+};
+
+pub fn main() {
+    let grid = day8::parse_grid(&util::parse_input());
+
+    let rows = grid.len();
+    assert!(rows > 0);
+    let cols = grid.get(0).unwrap().len();
+    assert!(cols > 0);
+
+    let max_score = (0..rows)
+        .map(move |r| (0..cols).map(move |c| (r, c)))
+        .flatten()
+        .map(|c| calc_scenic_score(&grid, c))
+        .max()
+        .unwrap();
+
+    println!("Max scenic score is {}", max_score);
+}

src/day8.rs

@@ -55,3 +55,38 @@ fn check_indices(grid: &Grid, coords: &mut dyn Iterator<Item = Coordinate>) -> V
 
     result
 }
+
+pub fn calc_scenic_score(grid: &Grid, (row, col): Coordinate) -> usize {
+    let rows = grid.len();
+    assert!(rows > 0);
+    let cols = grid.get(0).unwrap().len();
+    assert!(cols > 0);
+
+    let height = *grid.get(row).unwrap().get(col).unwrap();
+    let mut left = (0..col).map(|c| (row, c)).rev();
+    let mut right = (col + 1..cols).map(|c| (row, c));
+    let mut up = (0..row).map(|r| (r, col)).rev();
+    let mut down = (row + 1..rows).map(|r| (r, col));
+    let mut directions: Vec<&mut dyn Iterator<Item = Coordinate>> =
+        vec![&mut left, &mut right, &mut up, &mut down];
+    directions
+        .iter_mut()
+        .map(|d| calc_viewing_distance(grid, height, *d))
+        .product()
+}
+
+fn calc_viewing_distance(
+    grid: &Grid,
+    start_height: u32,
+    coords: &mut dyn Iterator<Item = Coordinate>,
+) -> usize {
+    let mut result = 0;
+    for (row, col) in coords {
+        result += 1;
+        let height = *grid.get(row).unwrap().get(col).unwrap();
+        if height >= start_height {
+            break;
+        }
+    }
+    result
+}