add day 17

day17/Cargo.lock

@@ -0,0 +1,16 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "day17"
+version = "0.1.0"
+dependencies = [
+ "md5",
+]
+
+[[package]]
+name = "md5"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ae960838283323069879657ca3de837e9f7bbb4c7bf6ea7f1b290d5e9476d2e0"

day17/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "day17"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+md5 = "*"

day17/src/main.rs

@@ -0,0 +1,154 @@
+use std::{
+    collections::{HashSet, VecDeque},
+    fmt::Display,
+};
+
+#[cfg(debug_assertions)]
+// const PASSCODE: &str = "ihgpwlah";
+const PASSCODE: &str = "ulqzkmiv";
+
+#[cfg(not(debug_assertions))]
+const PASSCODE: &str = "hhhxzeay";
+
+fn main() {
+    let state = State::new();
+
+    let result = bfs(state);
+    println!("{result}");
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+struct State {
+    route: Route,
+    position: (usize, usize),
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+struct Route(Vec<Direction>);
+
+impl Display for Route {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        for dir in &self.0 {
+            let the_char = match dir {
+                Direction::Up => 'U',
+                Direction::Down => 'D',
+                Direction::Left => 'L',
+                Direction::Right => 'R',
+            };
+            write!(f, "{the_char}")?;
+        }
+
+        Ok(())
+    }
+}
+
+impl Route {
+    fn new() -> Self {
+        Self(vec![])
+    }
+
+    fn push(&mut self, dir: Direction) {
+        self.0.push(dir);
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+enum Direction {
+    Up,
+    Down,
+    Left,
+    Right,
+}
+
+impl State {
+    fn new() -> Self {
+        Self {
+            route: Route::new(),
+            position: (0, 0),
+        }
+    }
+
+    fn is_goal_state(&self) -> bool {
+        self.position == (3, 3)
+    }
+
+    fn neighbor_states(&self, passcode: &str) -> impl Iterator<Item = State> {
+        let input = format!("{}{}", passcode, self.route);
+
+        let mut hash = format!("{:x}", md5::compute(input));
+        hash.truncate(4);
+
+        let possible_directions = self.generate_directions_from_hash(&hash);
+
+        let mut result = vec![];
+
+        for direction in possible_directions {
+            let mut new_state = self.clone();
+            new_state.update_position(&direction);
+
+            new_state.route.push(direction);
+            result.push(new_state)
+        }
+        result.into_iter()
+    }
+
+    fn generate_directions_from_hash(&self, hash: &str) -> impl Iterator<Item = Direction> {
+        hash.chars()
+            .zip([
+                Direction::Up,
+                Direction::Down,
+                Direction::Left,
+                Direction::Right,
+            ])
+            .filter(|(c, _)| ('b'..='f').contains(c))
+            .map(|(_, dir)| dir)
+            .filter(|dir| match dir {
+                Direction::Up => self.position.1 > 0,
+                Direction::Down => self.position.1 < 3,
+                Direction::Left => self.position.0 > 0,
+                Direction::Right => self.position.0 < 3,
+            })
+    }
+
+    fn update_position(&mut self, dir: &Direction) {
+        match *dir {
+            Direction::Up => {
+                self.position.1 -= 1;
+            }
+            Direction::Down => {
+                self.position.1 += 1;
+            }
+            Direction::Left => {
+                self.position.0 -= 1;
+            }
+            Direction::Right => {
+                self.position.0 += 1;
+            }
+        }
+    }
+}
+
+fn bfs(start: State) -> Route {
+    let mut queue = VecDeque::new();
+    let mut visited = HashSet::new();
+    visited.insert(start.clone());
+
+    queue.push_back(start);
+
+    while let Some(current_state) = queue.pop_front() {
+        if current_state.is_goal_state() {
+            // return current_state.route;
+            continue;
+        }
+
+        for neighbor in current_state.neighbor_states(PASSCODE) {
+            println!("{} {}", neighbor.route.0.len(), neighbor.is_goal_state());
+            if !visited.contains(&neighbor) {
+                visited.insert(neighbor.clone());
+                queue.push_back(neighbor);
+            }
+        }
+    }
+
+    panic!("goal state unreachable");
+}