day_6: part 2 done

README.md

@@ -8,7 +8,7 @@ https://adventofcode.com/2024
 | 03 | Mull It Over | :pushpin: | :pushpin: | Regex |
 | 04 | Ceres Search | :pushpin: | :pushpin: | Matrix multidirectional search |
 | 05 | Print Queue | :pushpin: | :pushpin: | Queue order |
-| 06 | Guard Gallivant | :pushpin: |  | 2D navigation |
+| 06 | Guard Gallivant | :pushpin: | :pushpin: | 2D navigation |
 | 07 |  |  |  | |
 | 08 |  |  |  | |
 | 09 |  |  |  | |

src/advent_of_code/fri_06.rs

@@ -48,6 +48,20 @@ impl Guard {
         false
     }
 
+    fn will_loop(&mut self, map: &FloorMap) -> bool {
+        let mut prev_positions: HashSet<(usize, usize, usize)> = HashSet::new();
+
+        while !self.step(map) {
+            let new_prev_position = (self.x, self.y, self.dir as usize);
+            if prev_positions.contains(&new_prev_position) {
+                return true;
+            }
+            prev_positions.insert(new_prev_position);
+        }
+
+        false
+    }
+
     fn turn_90(&mut self) {
         match self.dir {
             Direction::N => self.dir = Direction::E,
@@ -58,7 +72,7 @@ impl Guard {
     }
 }
 
-pub fn guard_gallivant(input: &str) -> PositionCount {
+pub fn guard_gallivant(input: &str) -> (PositionCount, usize) {
     let (mut the_guard, floor_map) = utils::read_floor_map_and_guard_input(input);
 
     let mut visited_coordinates: HashSet<(usize, usize)> = HashSet::new();
@@ -69,5 +83,16 @@ pub fn guard_gallivant(input: &str) -> PositionCount {
         visited_coordinates.insert((the_guard.x, the_guard.y));
     }
 
-    visited_coordinates.len()
+    let (the_guard, mut floor_map) = utils::read_floor_map_and_guard_input(input);
+    let mut loop_obstacles_count: usize = 0;
+    for visited in &visited_coordinates {
+        let mut temp_guard = the_guard.clone();
+        floor_map[visited.1][visited.0] = Floor::Obstacle;
+        if temp_guard.will_loop(&floor_map) {
+            loop_obstacles_count += 1;
+        }
+        floor_map[visited.1][visited.0] = Floor::Clear;
+    }
+
+    (visited_coordinates.len(), loop_obstacles_count)
 }

src/advent_of_code/mod.rs

@@ -14,41 +14,44 @@ pub fn today() {
 }
 
 pub fn historian_hysteria() {
+    // NOTE: previous days are commented to speed up (all the blame is on day 6)
     // Sunday 01
-    let key = sun_01::get_key("./assets/day_1_input").unwrap();
+    // let key = sun_01::get_key("./assets/day_1_input").unwrap();
-    println!("The key is: {key}");
+    // println!("The key is: {key}");
-    let similarity = sun_01::get_similarity("./assets/day_1_input");
+    // let similarity = sun_01::get_similarity("./assets/day_1_input");
-    println!("The similarity is: {similarity}");
+    // println!("The similarity is: {similarity}");
 
     // Monday 02
-    let safe_report_count = mon_02::check_reports_safety("./assets/day_2_reports_input");
+    // let safe_report_count = mon_02::check_reports_safety("./assets/day_2_reports_input");
-    println!("There are {safe_report_count} safe reports");
+    // println!("There are {safe_report_count} safe reports");
 
     // Tuesday 03
-    let multiplication_added_result = tue_03::mull_it_over("./assets/day_3_instruction_input");
+    // let multiplication_added_result = tue_03::mull_it_over("./assets/day_3_instruction_input");
-    println!(
+    // println!(
-        "The result of the sum of multiplications is {}",
+    //     "The result of the sum of multiplications is {}",
-        multiplication_added_result
+    //     multiplication_added_result
-    );
+    // );
-    let conditional_multiplication_added_result =
+    // let conditional_multiplication_added_result =
-        tue_03::mull_it_over_conditional("./assets/day_3_instruction_input");
+    //     tue_03::mull_it_over_conditional("./assets/day_3_instruction_input");
-    println!(
+    // println!(
-        "The result of the conditional sum of multiplications is {}",
+    //     "The result of the conditional sum of multiplications is {}",
-        conditional_multiplication_added_result
+    //     conditional_multiplication_added_result
-    );
+    // );
 
     // Wednesday 04
-    let (xmas_appearances, x_mas_appearances) = wed_04::ceres_search("./assets/day_4_input");
+    // let (xmas_appearances, x_mas_appearances) = wed_04::ceres_search("./assets/day_4_input");
-    println!("XMAS appears {} times", xmas_appearances);
+    // println!("XMAS appears {} times", xmas_appearances);
-    println!("X-MAS appears {} times", x_mas_appearances);
+    // println!("X-MAS appears {} times", x_mas_appearances);
 
     // Thursday 05
-    let (queue_mid_sum, fixed_queue_mid_sum) =
+    // let (queue_mid_sum, fixed_queue_mid_sum) =
-        thu_05::mid_queue_sum("./assets/day_5_rules_queue_input");
+    //     thu_05::mid_queue_sum("./assets/day_5_rules_queue_input");
-    println!("The update mid-queue-sum is {}", queue_mid_sum);
+    // println!("The update mid-queue-sum is {}", queue_mid_sum);
-    println!("The fixed update mid-queue-sum is {}", fixed_queue_mid_sum);
+    // println!("The fixed update mid-queue-sum is {}", fixed_queue_mid_sum);
 
     // Friday 06
-    let guard_position_count = fri_06::guard_gallivant("./assets/day_6_guard_map_input");
+    let (guard_position_count, loop_obstacle_count) =
+        fri_06::guard_gallivant("./assets/day_6_guard_map_input");
     println!("The guard will visit {} positions", guard_position_count);
+    println!("The guard would loop on {} positions", loop_obstacle_count);
 }

src/advent_of_code/types.rs

@@ -25,6 +25,7 @@ pub struct Rule(pub u32, pub u32);
 pub type Queue = Vec<u32>;
 
 // Guard Gallivant
+#[derive(Clone, Copy)]
 pub enum Direction {
     N,
     S,
@@ -38,6 +39,7 @@ pub enum Floor {
 pub type PositionCount = usize;
 pub type IsGuardOut = bool;
 pub type FloorMap = Vec<Vec<Floor>>;
+#[derive(Clone, Copy)]
 pub struct Guard {
     pub x: usize,
     pub y: usize,