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}")

03/py/test.py

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+from typing import ContextManager, Optional
+from solution import part1, part2, priority, threes
+
+from contextlib import nullcontext as no_raise
+
+import pytest
+
+
+@pytest.fixture
+def example_data() -> str:
+    return """vJrwpWtwJgWrhcsFMMfFFhFp
+jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
+PmmdzqPrVvPwwTWBwg
+wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
+ttgJtRGJQctTZtZT
+CrZsJsPPZsGzwwsLwLmpwMDw"""
+
+
+def test_part1(example_data: str) -> None:
+    assert part1(example_data) == 157
+
+
+@pytest.mark.parametrize(
+    "s,expected",
+    [
+        ("a", 1),
+        ("b", 2),
+        ("z", 26),
+        ("A", 27),
+        ("C", 29),
+        ("Z", 52),
+    ],
+)
+def test_priority(s: str, expected: int) -> None:
+    assert priority(s) == expected
+
+
+@pytest.mark.parametrize(
+    "line,expected,raises",
+    [
+        ("a\nb\nc", [("a", "b", "c")], no_raise()),
+        ("a\nb\nc\nd", None, pytest.raises(ValueError)),
+    ],
+)
+def test_threes(
+    line: str,
+    expected: Optional[list[tuple[str, str, str]]],
+    raises: ContextManager,
+):
+    with raises:
+        actual = list(threes(line.splitlines()))
+        if expected:
+            assert actual == expected
+
+
+def test_part2(example_data: str) -> None:
+    assert part2(example_data) == 70