Day 6 part 1 and 2, very rudimentary

src/day6.rs

@@ -0,0 +1,160 @@
+use std::collections::BTreeSet;
+use std::collections::HashMap;
+
+#[derive(Debug)]
+struct OrbitMap {
+    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>>())
+        .collect()
+}
+
+fn get_space_objects(input: &str) -> HashMap<String, usize> {
+    let items = input
+        .lines()
+        .map(|line| line.split(")").map(String::from).collect::<Vec<String>>())
+        .flatten();
+
+    let mut space_objects: HashMap<String, usize> = HashMap::new();
+    let mut n = 0;
+    items.for_each(|x| {
+        if !space_objects.contains_key(&x) {
+            space_objects.insert(x, n);
+            n += 1;
+        }
+    });
+    //println!("{:?}", space_objects);
+
+    space_objects
+}
+
+fn calculate_map(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);
+    (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!("part2 = {:?}", calculate_distance(input));
+    Ok(())
+}
+
+#[test]
+fn test_day6_part1() {
+    let input = "COM)B\n\
+                 B)C\n\
+                 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\
+                 B)C\n\
+                 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);
+}