Simplified day6 :)

src/day6.rs

@@ -1,160 +1,68 @@
-use std::collections::BTreeSet;
 use std::collections::HashMap;
+use std::iter::FromIterator;
 
-#[derive(Debug)]
+fn create_orbit_map(input: &str) -> HashMap<String, String> {
-struct OrbitMap {
+    let mut orbit_map: HashMap<String, String> = HashMap::new();
-    ids: Vec<usize>,
-}
-
-impl OrbitMap {
-    fn new(n: usize) -> Self {
-        Self {
-            ids: (0..n).collect::<Vec<usize>>(),
-        }
-    }
-
-    fn orbit_around(&mut self, base: usize, orbiter: usize) {
-        self.ids[orbiter] = base;
-        //println!("{:?}", self.ids);
-    }
-
-    fn range(&self, idx: usize) -> usize {
-        let mut i = idx;
-        let mut cnt = 0;
-        while i != self.ids[i] {
-            cnt += 1;
-            i = self.ids[i];
-        }
-        cnt
-    }
-
-    fn range_to(&self, idx: usize, limit: usize) -> usize {
-        let mut i = idx;
-        let mut cnt = 0;
-        while i != limit {
-            i = self.ids[i];
-            cnt += 1;
-        }
-        cnt - 1
-    }
-
-    fn path(&self, idx: usize) -> BTreeSet<usize> {
-        let mut i = idx;
-        let mut res = BTreeSet::new();
-        while i != self.ids[i] {
-            res.insert(i);
-            i = self.ids[i];
-        }
-        res
-    }
-
-    fn distance(&self, p: usize, q: usize) -> usize {
-        let ppath = self.path(p);
-        let qpath = self.path(q);
-        let common_roots = ppath.intersection(&qpath);
-
-        common_roots
-            .map(|cr| self.range_to(p, *cr) + self.range_to(q, *cr))
-            .min()
-            .unwrap()
-    }
-}
-
-fn get_pairs(input: &str) -> Vec<Vec<String>> {
     input
         .lines()
-        .map(|line| line.split(")").map(String::from).collect::<Vec<String>>())
+        .map(|line| line.split(")").map(String::from).collect())
-        .collect()
+        .for_each(|pair: Vec<String>| {
+            orbit_map.entry(pair[1].clone()).or_insert(pair[0].clone());
+        });
+    orbit_map
 }
 
-fn get_space_objects(input: &str) -> HashMap<String, usize> {
+fn part1(input: &str) -> usize {
-    let items = input
+    let orbit_map = create_orbit_map(input);
-        .lines()
-        .map(|line| line.split(")").map(String::from).collect::<Vec<String>>())
-        .flatten();
 
-    let mut space_objects: HashMap<String, usize> = HashMap::new();
+    let mut cnt: usize = 0;
-    let mut n = 0;
+    for obj in orbit_map.keys() {
-    items.for_each(|x| {
+        let mut key = obj;
-        if !space_objects.contains_key(&x) {
+        while let Some(val) = orbit_map.get(key) {
-            space_objects.insert(x, n);
+            cnt += 1;
-            n += 1;
+            key = val;
         }
-    });
+    }
-    //println!("{:?}", space_objects);
+    cnt
-
-    space_objects
 }
 
-fn calculate_map(input: &str) -> usize {
+fn part2(input: &str) -> usize {
-    let space_objects = get_space_objects(input);
+    let orbit_map = create_orbit_map(input);
-    let pairs = get_pairs(input);
-    let mut orbit_map = OrbitMap::new(space_objects.len());
 
-    for pair in pairs {
+    let my_traj: HashMap<String, usize> = HashMap::from_iter(
-        //println!("{:?}", pair);
+        std::iter::successors(orbit_map.get("YOU").map(|el| (el, 0)), |(nxt, n)| {
-        let base = space_objects.get(&pair[0]).unwrap();
+            (orbit_map.get(*nxt).map(|el| (el, n + 1 as usize)))
-        let orbiter = space_objects.get(&pair[1]).unwrap();
+        })
-        orbit_map.orbit_around(*base, *orbiter);
+        .map(|(el, n)| (String::from(el), n)),
+    );
+
+    let mut santa_transfers = 0;
+    let mut santa = orbit_map.get("SAN").unwrap();
+    loop {
+        if my_traj.contains_key(santa) {
+            return my_traj.get(santa).unwrap() + santa_transfers;
+        } else {
+            santa = orbit_map.get(santa).expect("no common orbits found");
+            santa_transfers += 1;
+        }
     }
-    //println!("{:?}", orbit_map.ids);
-    (0..orbit_map.ids.len()).map(|i| orbit_map.range(i)).sum()
-}
-
-fn calculate_distance(input: &str) -> usize {
-    let space_objects = get_space_objects(input);
-    let pairs = get_pairs(input);
-    let mut orbit_map = OrbitMap::new(space_objects.len());
-
-    for pair in pairs {
-        //println!("{:?}", pair);
-        let base = space_objects.get(&pair[0]).unwrap();
-        let orbiter = space_objects.get(&pair[1]).unwrap();
-        orbit_map.orbit_around(*base, *orbiter);
-    }
-    //println!("{:?}", orbit_map.ids);
-    let me = *space_objects.get("YOU").unwrap();
-    let santa = *space_objects.get("SAN").unwrap();
-    orbit_map.distance(me, santa)
 }
 
 pub fn main() -> std::io::Result<()> {
     let input = std::include_str!("../day6-input.txt").trim();
-    println!("part1 = {:?}", calculate_map(input));
+    println!("part1 = {:?}", part1(input));
-    println!("part2 = {:?}", calculate_distance(input));
+    println!("part2 = {:?}", part2(input));
     Ok(())
 }
 
 #[test]
 fn test_day6_part1() {
-    let input = "COM)B\n\
+    let input = "COM)B\nB)C\nC)D\nD)E\nE)F\nB)G\nG)H\nD)I\nE)J\nJ)K\nK)L";
-                 B)C\n\
+    assert_eq!(part1(input), 42);
-                 C)D\n\
-                 D)E\n\
-                 E)F\n\
-                 B)G\n\
-                 G)H\n\
-                 D)I\n\
-                 E)J\n\
-                 J)K\n\
-                 K)L";
-    assert_eq!(calculate_map(input), 42);
 }
 
 #[test]
 fn test_day6_part2() {
-    let input = "COM)B\n\
+    let input = "COM)B\nB)C\nC)D\nD)E\nE)F\nB)G\nG)H\nD)I\nE)J\nJ)K\nK)L\nK)YOU\nI)SAN";
-                 B)C\n\
+    assert_eq!(part2(input), 4);
-                 C)D\n\
-                 D)E\n\
-                 E)F\n\
-                 B)G\n\
-                 G)H\n\
-                 D)I\n\
-                 E)J\n\
-                 J)K\n\
-                 K)L\n\
-                 K)YOU\n\
-                 I)SAN";
-    assert_eq!(calculate_distance(input), 4);
 }