Bad day 6 solution.

day06/.gitignore

@@ -0,0 +1,2 @@
+target
+debug

day06/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "day06"
+version = "0.1.0"

day06/Cargo.toml

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+[package]
+name = "day06"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

day06/src/main.rs

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+use std::fs;
+
+#[derive(Debug, Clone, Copy)]
+enum Dir {
+    Up,
+    Down,
+    Left,
+    Right,
+}
+
+impl From<Dir> for i32 {
+    fn from(value: Dir) -> Self {
+        match value {
+            Dir::Up => 1,
+            Dir::Down => 2,
+            Dir::Left => 3,
+            Dir::Right => 4,
+        }
+    }
+}
+
+impl Dir {
+    fn move_point(&self, point: (usize, usize), max: (usize, usize)) -> Option<(usize, usize)> {
+        match self {
+            Dir::Up if point.1 > 0 => Some((point.0, point.1 - 1)),
+            Dir::Down if point.1 < max.1 => Some((point.0, point.1 + 1)),
+            Dir::Left if point.0 > 0 => Some((point.0 - 1, point.1)),
+            Dir::Right if point.0 < max.0 => Some((point.0 + 1, point.1)),
+            _ => None,
+        }
+    }
+
+    fn rotate(&self) -> Dir {
+        match self {
+            Dir::Up => Dir::Right,
+            Dir::Down => Dir::Left,
+            Dir::Left => Dir::Up,
+            Dir::Right => Dir::Down,
+        }
+    }
+}
+
+fn main() {
+    let input = fs::read_to_string("input.txt").unwrap();
+
+    let mut pos = (0, 0);
+    let mut dir = Dir::Up;
+    let mut no_edit_grid = input
+        .lines()
+        .filter(|&l| !l.is_empty())
+        .enumerate()
+        .map(|(y, l)| {
+            l.chars()
+                .enumerate()
+                .map(|(x, c)| match c {
+                    '#' => -1,
+                    '.' => 0,
+                    '^' => {
+                        pos = (x, y);
+                        0
+                    }
+                    _ => panic!("invalid char"),
+                })
+                .collect::<Vec<i32>>()
+        })
+        .collect::<Vec<Vec<i32>>>();
+    let original_grid = no_edit_grid.clone();
+    let oirignal_pos = pos;
+    let original_dir = dir;
+
+    loop {
+        no_edit_grid[pos.1][pos.0] = dir.into();
+        let next_pos =
+            match dir.move_point(pos, (no_edit_grid[0].len() - 1, no_edit_grid.len() - 1)) {
+                Some(p) => p,
+                None => break,
+            };
+
+        match no_edit_grid[next_pos.1][next_pos.0] {
+            -1 => dir = dir.rotate(),
+            _ => pos = next_pos,
+        }
+    }
+
+    println!(
+        "Part 1: {}",
+        no_edit_grid
+            .iter()
+            .map(|l| l.iter().filter(|&x| *x > 0).count())
+            .sum::<usize>()
+    );
+
+    let mut loops = -1;
+    for (x, y) in no_edit_grid
+        .iter()
+        .map(|l| {
+            l.iter().enumerate().filter_map(|(x, c)| match *c > 0 {
+                true => Some(x),
+                false => None,
+            })
+        })
+        .enumerate()
+        .flat_map(|(y, l)| l.map(move |x| (x, y)))
+    {
+        let mut edited_grid = original_grid.clone();
+        let mut pos = oirignal_pos;
+        let mut dir = original_dir;
+        edited_grid[y][x] = -1;
+
+        loop {
+            if (edited_grid[pos.1][pos.0] & (2 << i32::from(dir))) != 0 {
+                loops += 1;
+                break;
+            }
+            edited_grid[pos.1][pos.0] |= 2 << i32::from(dir);
+            let next_pos =
+                match dir.move_point(pos, (no_edit_grid[0].len() - 1, no_edit_grid.len() - 1)) {
+                    Some(p) => p,
+                    None => break,
+                };
+
+            match edited_grid[next_pos.1][next_pos.0] {
+                -1 => dir = dir.rotate(),
+                _ => pos = next_pos,
+            }
+        }
+    }
+
+    println!("Part 2: {}", loops);
+}