day08: Adapt code for part 2

I could probably optimize that by getting the iterators for all 4
directions and then to the scan on each of them in a loop, but I'm with
with this right now.

day08/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day08"
+version = "0.1.0"

day08/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day08"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day08/src/main.rs

@@ -0,0 +1,92 @@
+use std::error;
+use std::fs::File;
+use std::io::BufRead;
+use std::io::BufReader;
+
+fn main() -> Result<(), Box<dyn error::Error>> {
+	let f = File::open("input.txt")?;
+	let reader = BufReader::new(f);
+
+	let mut map = vec![];
+	let mut width = 0;
+	for line in reader.lines() {
+		let line = line?;
+
+		width = line.len();
+		map.extend(line.chars().map(|c| c.to_digit(10)).flatten().map(|d| d as usize));
+	}
+
+	let width = width;
+	let height = map.len() / width;
+
+	let mut scenic_scores = vec![];
+	for i in 0..map.len() {
+		let line = i / height;
+		let column = i % width + 1; // we need + 1 here, because there is no modulo 0
+		let mut scenic_score = 1;
+
+		// tree-houses cannot be built on the outside, so we have to skip those outside-trees for
+		// the calculation
+		if line == 0 || line == height - 1 || column == 1 || column == width {
+			continue;
+		}
+
+		// println!("line: {}, column: {}, self: {}", line, column, map[i]);
+		let left = map[(line * width)..i].iter()
+			.rev()
+			.scan(true, |state, &x| if !*state { None } else { if x >= map[i] { *state = false }; Some(1) })
+			// .inspect(|x| println!("{x}"))
+			.count();
+		if left > 0 {
+			scenic_score *= left;
+		}
+		let right = map[i..((line + 1) * width)].iter()
+			.enumerate()
+			.filter_map(|(j, x)| if (j + i) / height == line && j > 0 { Some(x) } else { None })
+			.scan(true, |state, &x| if !*state { None } else { if x >= map[i] { *state = false }; Some(1) })
+			.count();
+		if right > 0 {
+			scenic_score *= right;
+		}
+		// let right = map[(i + 1)..((line + 1) * width)].iter().max();
+		let up = map[0..i].iter()
+			.enumerate()
+			//.inspect(|(j, x)| println!("{j} {x}"))
+			.filter_map(|(j, x)| if (j + 1) % width == column { Some(x) } else { None })
+			.rev()
+			.scan(true, |state, &x| if !*state { None } else { if x >= map[i] { *state = false }; Some(1) })
+			.count();
+		if up > 0 {
+			scenic_score *= up;
+		}
+		let down = map[i..].iter()
+			.enumerate()
+			.filter_map(|(j, x)| if (i + j + 1) % width == column && j > 0 { Some(x) } else { None })
+			.scan(true, |state, &x| if !*state { None } else { if x >= map[i] { *state = false }; Some(1) })
+			.count();
+		if down > 0 {
+			scenic_score *= down;
+		}
+		// println!("left: {:?}, right: {:?}, up: {:?}, down: {:?}", &left, &right, &up, &down);
+
+		/*
+		for direction_max in vec![left, right, up, down] {
+			match direction_max {
+				Some(x) if x < &map[i] => {
+					visible_count += 1;
+					break;
+				},
+				None => {
+					visible_count += 1;
+					break;
+				},
+				_ => ()
+			}
+		}
+		*/
+		scenic_scores.push(scenic_score);
+	}
+
+    println!("Highest scenic score is {}", scenic_scores.iter().max().unwrap_or(&0));
+    Ok(())
+}