diff --git a/src/aoc_cj/aoc2019/day18.py b/src/aoc_cj/aoc2019/day18.py
index 31d7f2af..9d65561c 100644
--- a/src/aoc_cj/aoc2019/day18.py
+++ b/src/aoc_cj/aoc2019/day18.py
@@ -1,77 +1,92 @@
+import dataclasses
 import itertools
 from collections import deque
+from collections.abc import Generator
+from typing import TypeVar, Union
+
+import more_itertools as mi
 
 from aoc_cj import util
 
+Grid = dict[complex, str]
 
-def parse(txt: str):
-    grid = {complex(x, y): c for y, line in enumerate(txt.splitlines()) for x, c in enumerate(line)}
 
-    start_pos = next(p for p, c in grid.items() if c == "@")
-    num_keys = sum(1 for c in grid.values() if c.islower())
-    return grid, start_pos, num_keys
+@dataclasses.dataclass
+class StateA:
+    pos: complex
+    steps: int = 0
+    collected: frozenset[str] = frozenset()
 
+    def next_states(self: "StateA", grid: Grid) -> Generator["StateA", None, None]:
+        q = deque(((self.pos, self.steps),))
+        seen: set[complex] = set()
+        while len(q) > 0:
+            pos, steps = q.popleft()
+            if pos in seen:
+                continue
+            val = grid[pos]
+            if val in ".@" or val.lower() in self.collected:
+                q.extend((pos + delta, steps + 1) for delta in (-1j, 1, 1j, -1))
+            elif val != "#" and val.islower():
+                yield StateA(pos, steps, frozenset((*self.collected, val)))
+            seen.add(pos)
 
-def next_states_a(grid, state):
-    steps, pos, collected = state
-    q = deque()
-    q.append((pos, steps))
-    seen = set()
-    while len(q) > 0:
-        pos, steps = q.popleft()
-        if pos in seen:
-            continue
-        val: str = grid.get(pos)
-        if val in ".@" or val.lower() in collected:
-            q.extend((pos + delta, steps + 1) for delta in (-1j, 1, 1j, -1))
-        elif val != "#" and val.islower():
-            yield (steps, pos, frozenset((*collected, val)))
-        seen.add(pos)
-
-
-def next_states_b(grid, state):
-    steps, positions, collected = state
-    for i, pos in enumerate(positions):
-        for s in next_states_a(grid, (steps, pos, collected)):
-            new_steps, new_pos, new_collected = s
-            new_positions = list(positions)
-            new_positions[i] = new_pos
-            yield (new_steps, tuple(new_positions), new_collected)
-
-
-def search(initial, num_keys, grid, next_states=next_states_a):
-    q = util.PriorityQueue()
-    q.push(0, initial)
-    seen = set()
+
+@dataclasses.dataclass
+class StateB:
+    pos: tuple[complex, ...]
+    steps: int = 0
+    collected: frozenset[str] = frozenset()
+
+    def next_states(self, grid: Grid) -> Generator["StateB", None, None]:
+        for i, pos in enumerate(self.pos):
+            for new_state in StateA(pos, self.steps, self.collected).next_states(grid):
+                new_positions = list(self.pos)
+                new_positions[i] = new_state.pos
+                yield StateB(tuple(new_positions), new_state.steps, new_state.collected)
+
+
+# TODO: replace w/ protocol
+_TState = TypeVar("_TState", StateA, StateB)
+
+
+def search(start: _TState, grid: Grid) -> int:
+    all_keys = frozenset(c for c in grid.values() if c.islower())
+
+    q: util.PriorityQueue[_TState] = util.PriorityQueue()
+    q.push(0, start)
+    seen: set[tuple[Union[complex, tuple[complex, ...]], frozenset[str]]] = set()
     while q:
         state = q.pop()
-        steps, pos, collected = state
-        if len(collected) == num_keys:
-            return steps
-        if (pos, collected) in seen:
+        if (state.pos, state.collected) in seen:
             continue
-        for s in next_states(grid, state):
-            q.push(s[0], s)
-        seen.add((pos, collected))
-    return -1
+        # if all keys have been collected
+        if state.collected == all_keys:
+            return state.steps
+        for s in state.next_states(grid):
+            q.push(s.steps, s)
+        seen.add((state.pos, state.collected))
+    assert False, "unreachable"
 
 
-def parta(txt: str):
-    grid, start_pos, num_keys = parse(txt)
-    initial = (0, start_pos, frozenset())
-    return search(initial, num_keys, grid)
+def parta(txt: str) -> int:
+    grid = {complex(x, y): c for y, line in enumerate(txt.splitlines()) for x, c in enumerate(line)}
+    start_pos = mi.one(p for p, c in grid.items() if c == "@")
+
+    return search(StateA(start_pos), grid)
 
 
-def partb(txt: str):
-    grid, start_pos, num_keys = parse(txt)
+def partb(txt: str) -> int:
+    grid = {complex(x, y): c for y, line in enumerate(txt.splitlines()) for x, c in enumerate(line)}
+    start_pos = mi.one(p for p, c in grid.items() if c == "@")
 
     # update the cave entrance
     replace = "@#@\n###\n@#@".splitlines()
     for x, y in itertools.product(range(3), repeat=2):
         grid[start_pos + complex(x - 1, y - 1)] = replace[y][x]
 
-    initial = (0, tuple(start_pos + delta for delta in (-1 - 1j, 1 - 1j, 1 + 1j, -1 + 1j)), frozenset())
-    return search(initial, num_keys, grid, next_states_b)
+    start = tuple(start_pos + delta for delta in (-1 - 1j, 1 - 1j, 1 + 1j, -1 + 1j))
+    return search(StateB(start), grid)
 
 
 if __name__ == "__main__":
diff --git a/tests/aoc2019/y2019d18_test.py b/tests/aoc2019/y2019d18_test.py
index 20e9ff62..3be1850b 100644
--- a/tests/aoc2019/y2019d18_test.py
+++ b/tests/aoc2019/y2019d18_test.py
@@ -98,7 +98,7 @@
         (EXAMPLE_INPUT_A4, 81),
     ],
 )
-def test_a(input, expected):
+def test_a(input: str, expected: int) -> None:
     assert d.parta(input) == expected
 
 
@@ -111,5 +111,5 @@ def test_a(input, expected):
         (EXAMPLE_INPUT_B4, 72),
     ],
 )
-def test_b(input, expected):
+def test_b(input: str, expected: int) -> None:
     assert d.partb(input) == expected