Python: Day 3

03/py/solution.py

@@ -0,0 +1,65 @@
+from pathlib import Path
+from typing import Generator, TypeVar
+from collections.abc import Iterable
+
+
+T = TypeVar("T")
+
+
+def threes(i: Iterable[T]) -> Generator[tuple[T, T, T], None, None]:
+    if len(i) % 3 != 0:
+        raise ValueError()
+
+    for idx in range(0, len(i), 3):
+        yield i[idx], i[idx + 1], i[idx + 2]
+
+
+def priority(s: str) -> int:
+    assert len(s) == 1
+    if "a" <= s <= "z":
+        return ord(s) - ord("a") + 1
+    elif "A" <= s <= "Z":
+        return ord(s) - ord("A") + 27
+    raise RuntimeError(f"Invalid char: {s}")
+
+
+def split(s: str) -> tuple[str, str]:
+    mid = len(s) // 2
+    return s[:mid], s[mid:]
+
+
+def part1(data: str) -> int:
+    result = 0
+    for line in data.splitlines():
+        left, right = split(line)
+        both = {ch for ch in right}.intersection({ch for ch in left})
+        value = 0
+        for ch in both:
+            value += priority(ch)
+        print(f"{line}: {both}")
+        result += value
+    return result
+
+
+def part2(data: str) -> int:
+    result = 0
+    lines = data.splitlines()
+    for a, b, c in threes(lines):
+        badge = set(a).intersection(set(b)).intersection(set(c))
+        value = 0
+        for ch in badge:
+            value += priority(ch)
+        result += value
+    return result
+
+
+# Setup
+data = (Path(__file__).parents[1] / "input").read_text()
+
+# Problem solving - part 1
+result = part1(data)
+print(f"Part 1 solution: {result}")
+
+# Problem solving - part 2
+result = part2(data)
+print(f"Part 2 solution: {result}")