2015 day 3.

src/holt59/aoc/2015/day3.py

@@ -0,0 +1,34 @@
+import sys
+from collections import defaultdict
+
+line = sys.stdin.read().strip()
+
+
+def process(directions: str) -> dict[tuple[int, int], int]:
+    counts: dict[tuple[int, int], int] = defaultdict(lambda: 0)
+    counts[0, 0] = 1
+    x, y = (0, 0)
+
+    for c in directions:
+        match c:
+            case ">":
+                x += 1
+            case "<":
+                x -= 1
+            case "^":
+                y -= 1
+            case "v":
+                y += 1
+            case _:
+                raise ValueError()
+
+        counts[x, y] += 1
+
+    return counts
+
+
+answer_1 = len(process(line))
+print(f"answer 1 is {answer_1}")
+
+answer_2 = len(process(line[::2]) | process(line[1::2]))
+print(f"answer 2 is {answer_2}")

src/holt59/aoc/__main__.py

@@ -12,6 +12,12 @@ def main():
     parser.add_argument(
         "-u", "--user", type=str, default="holt59", help="user input to use"
     )
+    parser.add_argument(
+        "--stdin",
+        action="store_true",
+        default=False,
+        help="use stdin as input",
+    )
     parser.add_argument(
         "-i",
         "--input",
@@ -26,6 +32,7 @@ def main():
 
     verbose: bool = args.verbose
     test: bool = args.test
+    stdin: bool = args.stdin
     user: str = args.user
     input_path: Path | None = args.input
 
@@ -42,8 +49,11 @@ def main():
         )
     assert input_path.exists(), f"{input_path} missing"
 
-    with open(input_path) as fp:
+    if stdin:
-        sys.stdin = fp
         importlib.import_module(f".{year}.day{day}", __package__)
+    else:
+        with open(input_path) as fp:
+            sys.stdin = fp
+            importlib.import_module(f".{year}.day{day}", __package__)
 
-    sys.stdin = sys.__stdin__
+        sys.stdin = sys.__stdin__