day 6

src/main.rs

@@ -2,10 +2,7 @@ use ansi_term::enable_ansi_support;
 use aoc2024::{
     cli::AocCli,
     map_solution,
-    solutions::{
-        AocDayFiveSolution, AocDayFourSolution, AocDayOneSolution, AocDayThreeSolution,
-        AocDayTwoSolution, AocSolution,
-    },
+    solutions::*,
     utils::{Error, Result},
 };
 use clap::Parser;
@@ -30,6 +27,7 @@ fn main() -> Result<()> {
         3 => AocDayThreeSolution,
         4 => AocDayFourSolution,
         5 => AocDayFiveSolution,
+        6 => AocDaySixSolution,
     };
 
     Ok(())

src/solutions/day_6.rs

@@ -1 +1,109 @@
+use std::{
+    collections::{HashMap, HashSet},
+    fs::read_to_string,
+    path::Path,
+};
+
+use super::AocSolution;
+use crate::utils::{coord::Coord, direction::Direction, Result};
+
+#[derive(Debug, Clone)]
+struct Guard {
+    dir: Direction,
+    cur: Coord,
+    grid: HashMap<Coord, bool>,
+}
+
+impl Guard {
+    fn new(src: &str) -> Self {
+        let (grid, cur) = src
+            .lines()
+            .zip(0..)
+            .flat_map(|(l, y)| {
+                l.chars()
+                    .zip(0..)
+                    .map(move |(ch, x)| (Coord::new(x, y), ch))
+            })
+            .fold(
+                (HashMap::new(), Coord::new(0, 0)),
+                |(mut map, coord), (crd, obs)| {
+                    map.insert(crd, obs == '#');
+                    let coord = if obs == '^' { crd } else { coord };
+                    (map, coord)
+                },
+            );
+
+        Self {
+            dir: Direction::default(),
+            cur,
+            grid,
+        }
+    }
+
+    fn patrol(&mut self) -> (usize, bool) {
+        let mut repetition = 0u16;
+        let mut flag = false;
+        let mut patrolled = HashSet::new();
+
+        loop {
+            if repetition == 65535 {
+                flag = true;
+                break;
+            }
+
+            let lookahead = self.cur + self.dir;
+            if let Some(&obs) = self.grid.get(&lookahead) {
+                if obs {
+                    self.dir.turn_right();
+                } else {
+                    if !patrolled.insert(self.cur) {
+                        repetition += 1;
+                    };
+                    self.cur = lookahead;
+                }
+            } else {
+                break;
+            }
+        }
+
+        (patrolled.len() + 1, flag)
+    }
+
+    fn loop_prank(&mut self) -> u64 {
+        let mut total = 0;
+        for &key in self.grid.keys() {
+            let mut tmp = self.clone();
+            if tmp.grid.get(&key).is_some_and(|cond| !*cond) {
+                tmp.grid.insert(key, true);
+                if tmp.patrol().1 {
+                    total += 1;
+                }
+            };
+        }
+
+        total
+    }
+}
+
+#[derive(Clone, Copy)]
 pub struct AocDaySixSolution;
+
+impl AocSolution for AocDaySixSolution {
+    type Output = u64;
+    fn get_input(&self, path: Option<&Path>) -> Result<String> {
+        match path {
+            Some(p) => Ok(read_to_string(p)?),
+            None => Ok(read_to_string("./input/day_6.txt")?),
+        }
+    }
+
+    fn part_one(&self, input: &str) -> Result<Self::Output> {
+        let mut g = Guard::new(input);
+        Ok(g.patrol().0 as Self::Output)
+    }
+
+    fn part_two(&self, input: &str) -> Result<Self::Output> {
+        let mut g = Guard::new(input);
+        Ok(g.loop_prank())
+    }
+}

src/utils/coord.rs

@@ -0,0 +1,32 @@
+use std::ops::Add;
+
+use super::direction::Direction;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Coord {
+    pub x: i16,
+    pub y: i16,
+}
+
+impl Coord {
+    pub fn new(x: i16, y: i16) -> Self {
+        Self { x, y }
+    }
+}
+
+impl Add for Coord {
+    type Output = Coord;
+
+    fn add(self, rhs: Self) -> Self::Output {
+        Self::new(self.x + rhs.x, self.y + rhs.y)
+    }
+}
+
+impl Add<Direction> for Coord {
+    type Output = Coord;
+
+    fn add(self, rhs: Direction) -> Self::Output {
+        let tmp = rhs.lookahead();
+        self + tmp
+    }
+}

src/utils/direction.rs

@@ -0,0 +1,66 @@
+use std::ops::{Neg, Not};
+
+use super::coord::Coord;
+
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum Direction {
+    #[default]
+    Up,
+    Right,
+    Left,
+    Down,
+}
+
+impl Direction {
+    pub fn turn_right(&mut self) {
+        match self {
+            Self::Up => *self = Self::Right,
+            Self::Right => *self = Self::Down,
+            Self::Down => *self = Self::Left,
+            Self::Left => *self = Self::Up,
+        }
+    }
+
+    pub fn turn_left(&mut self) {
+        match self {
+            Self::Up => *self = Self::Left,
+            Self::Left => *self = Self::Down,
+            Self::Down => *self = Self::Right,
+            Self::Right => *self = Self::Up,
+        }
+    }
+
+    pub fn turn_back(&mut self) {
+        *self = !*self
+    }
+
+    pub fn lookahead(&self) -> Coord {
+        match self {
+            Self::Up => Coord::new(0, -1),
+            Self::Right => Coord::new(1, 0),
+            Self::Down => Coord::new(0, 1),
+            Self::Left => Coord::new(-1, 0),
+        }
+    }
+}
+
+impl Not for Direction {
+    type Output = Self;
+
+    fn not(self) -> Self::Output {
+        match self {
+            Self::Up => Self::Down,
+            Self::Left => Self::Right,
+            Self::Down => Self::Up,
+            Self::Right => Self::Left,
+        }
+    }
+}
+
+impl Neg for Direction {
+    type Output = Self;
+
+    fn neg(self) -> Self::Output {
+        !self
+    }
+}

src/utils/mod.rs

@@ -1,6 +1,9 @@
 #[macro_use]
 pub mod macros;
 
+pub mod coord;
+pub mod direction;
+
 pub type Result<T> = std::result::Result<T, Error>;
 
 #[derive(thiserror::Error, Debug)]