day20 part 2

src/tasks/day20.rs

@@ -1,9 +1,8 @@
 use self::Tile::*;
 #[allow(unused_imports)]
 use crate::utils;
-use std::collections::{HashMap, HashSet};
-use std::ops::Add;
 use std::collections::VecDeque;
+use std::collections::{HashMap, HashSet};
 
 pub fn task1() {
     let input = utils::read_file("input/day20.txt");
@@ -15,7 +14,14 @@ pub fn task1() {
 
     // print_map(&map);
 
-    println!("Most distant point: {:?}", longest_shortest_path(&map, Point(0,0)));
+    println!(
+        "Most distant point: {:?}",
+        longest_shortest_path(&map, Point(0, 0))
+    );
+    println!(
+        "Rooms with minimal distance >= 1000: {}",
+        count_long_distances(&map, Point(0, 0), 1000)
+    );
 }
 
 /// Returns the end points of the parsed input
@@ -23,7 +29,7 @@ fn parse_input(map: &mut HashMap<Point, Tile>, input: &str, position: Point) ->
     // println!("{}, {:?}", input, position);
     if input == "$" {
         println!("End of the road.");
-        return vec!(position).into_iter().collect();
+        return vec![position].into_iter().collect();
     }
     let mut position = position;
     let mut input = input;
@@ -81,7 +87,7 @@ fn parse_input(map: &mut HashMap<Point, Tile>, input: &str, position: Point) ->
             ),
         }
     }
-    vec!(position).into_iter().collect()
+    vec![position].into_iter().collect()
 }
 
 /// Splits the input by '|', but only by those that are not enclosed by further parenthesises.
@@ -167,9 +173,9 @@ fn print_map(map: &HashMap<Point, Tile>) {
 
 fn longest_shortest_path(map: &HashMap<Point, Tile>, start: Point) -> Option<(Point, usize)> {
     let mut distances: HashMap<Point, usize> = HashMap::with_capacity(map.len());
-    let mut open: VecDeque<(usize,Point)> = VecDeque::new();
+    let mut open: VecDeque<(usize, Point)> = VecDeque::new();
     let mut visited: HashSet<Point> = HashSet::new();
-    open.push_back((0,start));
+    open.push_back((0, start));
     visited.insert(start);
     while let Some((distance, predecessor)) = open.pop_front() {
         distances.insert(predecessor, distance);
@@ -178,7 +184,7 @@ fn longest_shortest_path(map: &HashMap<Point, Tile>, start: Point) -> Option<(Po
                 let room = predecessor.next_room(&p);
                 if !visited.contains(&room) {
                     visited.insert(room);
-                open.push_back((distance + 1, room));
+                    open.push_back((distance + 1, room));
                 }
             }
         }
@@ -190,6 +196,30 @@ fn longest_shortest_path(map: &HashMap<Point, Tile>, start: Point) -> Option<(Po
     }
 }
 
+fn count_long_distances(map: &HashMap<Point, Tile>, start: Point, threshold: usize) -> usize {
+    let mut distances: HashMap<Point, usize> = HashMap::with_capacity(map.len());
+    let mut open: VecDeque<(usize, Point)> = VecDeque::new();
+    let mut visited: HashSet<Point> = HashSet::new();
+    open.push_back((0, start));
+    visited.insert(start);
+    while let Some((distance, predecessor)) = open.pop_front() {
+        distances.insert(predecessor, distance);
+        for p in predecessor.neighbors() {
+            if let Some(Door) = map.get(&p) {
+                let room = predecessor.next_room(&p);
+                if !visited.contains(&room) {
+                    visited.insert(room);
+                    open.push_back((distance + 1, room));
+                }
+            }
+        }
+    }
+    distances
+        .iter()
+        .filter(|(_, distance)| **distance >= threshold)
+        .count()
+}
+
 #[derive(Eq, PartialEq, Hash, Clone, Copy, Debug)]
 struct Point(i32, i32);
 
@@ -213,7 +243,10 @@ impl Point {
     }
 
     fn next_room(&self, other: &Self) -> Self {
-        Point(self.0 + 2*(other.0 - self.0), self.1 +2*(other.1-self.1))
+        Point(
+            self.0 + 2 * (other.0 - self.0),
+            self.1 + 2 * (other.1 - self.1),
+        )
     }
 }