done with part 2

2022-aoc/src/d8.rs

@@ -5,7 +5,6 @@ use aoc_runner_derive::{aoc as aoc_run, aoc_generator};
 use ndarray::prelude::*;
 
 type Forest = Array2<i8>;
-type Tree = (i8, i8);
 
 #[aoc_generator(day8)]
 fn parse_input_day1(input: &str) -> Forest {
@@ -77,5 +76,38 @@ fn part1(input: &Forest) -> usize {
 
 #[aoc_run(day8, part2)]
 fn part2(input: &Forest) -> usize {
-    0
+    let nrows = input.nrows();
+    let ncols = input.ncols();
+    let mut max = 0;
+    for row in 0..nrows {
+        for col in 0..ncols {
+            let (e, w) = check_span(col, &input.row(row));
+            let (n, s) = check_span(row, &input.column(col));
+            max = (e * w * n * s).max(max);
+        }
+    }
+    max
+}
+
+fn check_span(addr: usize, span: &ArrayView1<i8>) -> (usize, usize) {
+    let height = span[addr];
+    let (mut a, mut b) = (0, 0);
+    //
+    let neg = span.slice(s![0..addr]);
+    let pos = span.slice(s![addr..]);
+    for e in neg.iter().rev() {
+        a += 1;
+        if *e >= height {
+            break;
+        }
+    }
+
+    for e in pos.iter().skip(1) {
+        b += 1;
+        if *e >= height {
+            break;
+        }
+    }
+
+    (a, b)
 }