diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index d3d4b22..c646087 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -113,3 +113,8 @@ day-22:
   stage: build
   script:
     - cd day22; cargo run --release ./input
+
+day-23:
+  stage: build
+  script:
+    - cd day23; cargo run --release ./input
diff --git a/day23/Cargo.toml b/day23/Cargo.toml
new file mode 100644
index 0000000..3e1aa7d
--- /dev/null
+++ b/day23/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "day23"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/day23/input b/day23/input
new file mode 100644
index 0000000..64ceab9
--- /dev/null
+++ b/day23/input
@@ -0,0 +1,5 @@
+#############
+#...........#
+###A#D#B#D###
+  #B#C#A#C#
+  #########
diff --git a/day23/src/main.rs b/day23/src/main.rs
new file mode 100644
index 0000000..5ad88d0
--- /dev/null
+++ b/day23/src/main.rs
@@ -0,0 +1,215 @@
+use std::{fs, env, collections::{HashSet, HashMap}};
+
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+enum Amphipod {
+    Amber,
+    Bronze,
+    Copper,
+    Desert,
+    Placeholder
+}
+
+impl Amphipod {
+    fn get_target_room(&self) -> usize {
+        return match self {
+            Amphipod::Amber => { 0 }
+            Amphipod::Bronze => { 1 }
+            Amphipod::Copper => { 2 }
+            Amphipod::Desert => { 3 }
+            _ => { panic!("Amphipod has no target room.") }
+        };
+    }
+
+    fn get_from_str(s: &str) -> Amphipod {
+        return match s {
+            "A" => { Amphipod::Amber }
+            "B" => { Amphipod::Bronze }
+            "C" => { Amphipod::Copper }
+            "D" => { Amphipod::Desert }
+            _ => { panic!("Amphipod not recognized.") }
+        };
+    }
+}
+
+type Action = ((usize, bool), (usize, bool), u32);
+
+fn read_input(path: &str) -> String {
+    return fs::read_to_string(path).expect("Cannot read file.");
+}
+
+fn parse_input(s: &str) -> Vec<Vec<Amphipod>> {
+    let l = s.lines().skip(2)
+        .map(|l| l.trim().split("#").filter(|e| !e.is_empty())
+             .collect::<Vec<&str>>())
+        .filter(|e| !e.is_empty())
+        .collect::<Vec<Vec<&str>>>();
+    let mut g = vec![
+        vec![Amphipod::Placeholder; l.len()];
+        l.iter().fold(0, |acc, e| std::cmp::max(e.len(), acc))];
+    for (n, v) in l.iter().rev().enumerate() {
+        for (i, a) in v.iter().enumerate() {
+            g[i][n] = Amphipod::get_from_str(*a);
+        }
+    }
+    return g;
+}
+
+fn expand_input(r: &mut Vec<Vec<Amphipod>>) {
+    let mut s = vec![
+        Amphipod::Amber, Amphipod::Copper,
+        Amphipod::Bronze, Amphipod::Amber,
+        Amphipod::Copper, Amphipod::Bronze,
+        Amphipod::Desert, Amphipod::Desert];
+    for e in r.iter_mut() {
+        e.insert(1, s.pop().unwrap());
+        e.insert(2, s.pop().unwrap());
+    }
+}
+
+fn no_need_to_move(r: &Vec<Vec<Amphipod>>) -> HashSet<(usize, usize)> {
+    let mut h = HashSet::new();
+    for (i, v) in r.iter().enumerate() {
+        for (l, a) in v.iter().enumerate() {
+            if a.get_target_room() == i && (l == 0 || h.contains(&(i, l - 1))) {
+                h.insert((i, l));
+            }
+        }
+    }
+    return h;
+}
+
+fn is_room_full(rooms: &Vec<Vec<Amphipod>>, n: usize, s: &HashSet<(usize, usize)>,
+                room_depth: usize) -> bool {
+    return rooms[n].len() == room_depth
+        && s.iter().filter(|e| e.0 == n).count() == room_depth;
+}
+
+fn is_target_room_ready(rooms: &Vec<Vec<Amphipod>>, n: usize, s: &HashSet<(usize, usize)>,
+                        room_depth: usize) -> bool {
+    return !is_room_full(rooms, n, s, room_depth)
+        && s.iter().filter(|e| e.0 == n).count() == rooms[n].len();
+}
+
+fn can_cross_hallway(s: usize, t: usize, h: &Vec<Option<Amphipod>>) -> bool {
+    if h.iter().all(|e| e.is_none()) { return true; }
+    if s == t { return false; }
+    let (b, e) = (std::cmp::min(s, t) + 1, std::cmp::max(s, t));
+    return (b..e).all(|e| h[e].is_none());
+}
+
+fn room_to_hallway_pos(n: usize) -> usize {
+    return n * 2 + 2;
+}
+
+fn get_move_cost(f: &(usize, bool), t: &(usize, bool), r: &Vec<Vec<Amphipod>>,
+                 d: usize, a: &Amphipod) -> u32 {
+    let s = if f.1 { room_to_hallway_pos(f.0) } else { f.0 } as i32;
+    let e = if t.1 { room_to_hallway_pos(t.0) } else { t.0 } as i32;
+    return ((s - e).abs() as u32
+        + if f.1 { (d - r[f.0].len()) as u32 + 1 } else { 0 }
+        + if t.1 { (d - r[t.0].len()) as u32 } else { 0 })
+        * 10u32.pow(a.get_target_room() as u32);
+}
+
+fn get_next_moves(rs: &Vec<Vec<Amphipod>>, d: usize, h: &Vec<Option<Amphipod>>,
+                  s: &HashSet<(usize, usize)>) -> Vec<Action>{
+    let f = (0..rs.len()).map(|e| room_to_hallway_pos(e)).collect::<Vec<usize>>();
+    let mut a = vec![];
+    for (i, e) in h.iter().enumerate() {
+        if e.is_none() { continue; }
+        let e = e.unwrap();
+        let t = e.get_target_room();
+        if is_target_room_ready(rs, t, s, d)
+            && can_cross_hallway(i, room_to_hallway_pos(t), h) {
+            return vec![((
+                    (i, false),
+                    (t, true),
+                    get_move_cost(&(i, false), &(t, true), rs, d, &e)
+                          ))];
+        }
+    }
+    for (n, r) in rs.iter().enumerate() {
+        if r.is_empty() { continue; }
+        let l = r.last().unwrap();
+        let t = l.get_target_room();
+        if l.get_target_room() != n
+            && is_target_room_ready(rs, t, s, d)
+            && can_cross_hallway(room_to_hallway_pos(n), room_to_hallway_pos(t), h) {
+                return vec![((
+                        (n, true),
+                        (t, true),
+                        get_move_cost(&(n, true), &(t, true), rs, d, &l))
+                             )];
+        }
+        if !is_room_full(rs, n, s, d) && !is_target_room_ready(rs, n, s, d) {
+            for (j, o) in h.iter().enumerate() {
+                if o.is_some() || f.contains(&j) { continue; }
+                if can_cross_hallway(room_to_hallway_pos(n), j, h) {
+                    a.push((
+                            (n, true),
+                            (j, false),
+                            get_move_cost(&(n, true), &(j, false), rs, d, &l)));
+                }
+            }
+        }
+    }
+    return a;
+}
+
+fn apply_action(a: &Action, r: &mut Vec<Vec<Amphipod>>, s: &mut u32,
+                h: &mut Vec<Option<Amphipod>>) {
+    *s += a.2;
+    let o;
+    if a.0.1 {
+        o = r[a.0.0].pop().unwrap();
+    } else {
+        o = h[a.0.0].unwrap();
+        h[a.0.0] = None;
+    }
+    if a.1.1 {
+        r[a.1.0].push(o);
+    } else {
+        h[a.1.0] = Some(o);
+    }
+}
+
+fn compute_sorting(mut r: Vec<Vec<Amphipod>>, mut h: Vec<Option<Amphipod>>, d: usize,
+                   mut s: u32, b: &mut u32, a: &Action,
+                   c: &mut HashMap<(Vec<Vec<Amphipod>>, Vec<Option<Amphipod>>), u32>) -> Option<u32> {
+    apply_action(a, &mut r, &mut s, &mut h);
+    if s >= *c.get(&(r.clone(), h.clone())).unwrap_or(&u32::MAX) { return None; }
+    c.insert((r.clone(), h.clone()), s);
+    let n = no_need_to_move(&r);
+    if n.len() == r.len() * d {
+        *b = s;
+        return Some(s);
+    }
+    let m = get_next_moves(&r, d, &h, &n);
+    if m.is_empty() { return None; }
+    let mut o = None;
+    for mo in m {
+        let x = compute_sorting(r.clone(), h.clone(), d, s, b, &mo, c);
+        if x.is_some() && (o.is_none() || x.unwrap() < o.unwrap()) { o = x; }
+    }
+    return o;
+}
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    for arg in args.iter().skip(1) {
+        let input = read_input(&arg);
+        let mut vec_in = parse_input(&input);
+        let (mut s1, mut s2) = (u32::MAX, u32::MAX);
+        let a = ((0, true), (0, true), 0);
+        let mut c = HashMap::new();
+        let h = vec![None; 11];
+        compute_sorting(vec_in.clone(), h.clone(), 2, 0, &mut s1, &a, &mut c);
+        expand_input(&mut vec_in);
+        c.clear();
+        compute_sorting(vec_in, h, 4, 0, &mut s2, &a, &mut c);
+        println!("[{}]", &arg);
+        println!("\t[Part 1] => Answer is '{}'.", s1);
+        println!("\t[Part 2] => Answer is '{}'.", s2);
+    }
+}
+