Tidy up 2023/16 logic

IsaacG · Dec 16, 2023 · 9d83922 · 9d83922
1 parent aaa6995
commit 9d83922
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Showing 2 changed files with 39 additions and 20 deletions.
diff --git a/2023/16.py b/2023/16.py
@@ -39,30 +39,35 @@ def energized(self, parsed_input: InputType, start_pos, start_dir) -> int:
                 if (char := parsed_input.get(pos, None)) is None:
                     # Off the map.
                     pass
-                elif (
-                    char == "."
-                    or (char == "|" and direction in (UP, DOWN))
-                    or (char == "-" and direction in (RIGHT, LEFT))
-                ):
+                elif char == ".":
                     # Pass through empty space and pointy side of splitters.
                     new_beams.add((pos, direction))
                 elif char == "|":
-                    # Split.
-                    new_beams.add((pos, UP))
-                    new_beams.add((pos, DOWN))
+                    if direction in (UP, DOWN):
+                        new_beams.add((pos, direction))
+                    else:
+                        # Split.
+                        new_beams.add((pos, UP))
+                        new_beams.add((pos, DOWN))
                 elif char == "-":
-                    # Split.
-                    new_beams.add((pos, RIGHT))
-                    new_beams.add((pos, LEFT))
-                elif (
-                    (char == "/" and direction in (RIGHT, LEFT))
-                    or (char == "\\" and direction in (UP, DOWN))
-                ):
-                    # Rotate counter-clockwise.
-                    new_beams.add((pos, direction * -1j))
-                else:
-                    # Rotate clockwise.
-                    new_beams.add((pos, direction * 1j))
+                    if direction in (RIGHT, LEFT):
+                        new_beams.add((pos, direction))
+                    else:
+                        # Split.
+                        new_beams.add((pos, RIGHT))
+                        new_beams.add((pos, LEFT))
+                elif char == "/":
+                    # Rotate.
+                    if direction in (RIGHT, LEFT):
+                        new_beams.add((pos, direction * -1j))
+                    else:
+                        new_beams.add((pos, direction * +1j))
+                elif char == "\\":
+                    # Rotate.
+                    if direction in (RIGHT, LEFT):
+                        new_beams.add((pos, direction * +1j))
+                    else:
+                        new_beams.add((pos, direction * -1j))
             # Ignore already-handled beams (loop detection).
             beams = new_beams - seen
             seen.update(new_beams)

diff --git a/2023/notes.md b/2023/notes.md
@@ -173,3 +173,17 @@ My part 1 solution was decently fast to pass the example.
 However, it took me the longest time to figure out why it failed the real input.
 I seeded my data with a beam at `(0, 0) RIGHT` then loop where I examine the next time.
 This was fine in the example with `(0, 0)` is empty but the real data has a reflector at `(0, 0)` which I skipped.
+
+The massive logic block could be changed to a dictionary lookup but that bumps runtime from 8s to 11s.
+
+```python
+# Out direction(s) based on in direction.
+DIR_IN_TO_OUT = {
+    "#":  {direction: {} for direction in aoc.FOUR_DIRECTIONS},
+    ".":  {direction: {direction} for direction in aoc.FOUR_DIRECTIONS},
+    "|":  {UP: {UP}, DOWN: {DOWN}, RIGHT: {UP, DOWN}, LEFT: {UP, DOWN}},
+    "-":  {RIGHT: {RIGHT}, LEFT: {LEFT}, UP: {RIGHT, LEFT}, DOWN: {RIGHT, LEFT}},
+    "/":  {RIGHT: {UP}, LEFT: {DOWN}, UP: {RIGHT}, DOWN: {LEFT}},
+    "\\": {RIGHT: {DOWN}, LEFT: {UP}, UP: {LEFT}, DOWN: {RIGHT}},
+}
+```