feat: aoc 2025 day 12 solution + tests

Author: mbrickerd

_2025/solutions/day12.py

@@ -0,0 +1,87 @@
+"""Day 12: Christmas Tree Farm
+
+This module provides the solution for Advent of Code 2025 - Day 12.
+
+The input describes oddly-shaped presents and the rectangular regions
+under Christmas trees where those presents need to fit.
+
+This implementation uses a simplified feasibility check: it parses all
+present shapes, then for each region computes how much area the listed
+presents would require and compares it against the region area.
+"""
+
+from aoc.models.base import SolutionBase
+
+
+class Solution(SolutionBase):
+    """Check which tree regions are large enough for their present lists.
+
+    The puzzle input is split into two sections separated by a blank line:
+
+    - The first section lists present shapes, each starting with an index
+      line (`0:`, `1:`, ...) followed by a small ASCII-art block of `#`
+      and `.` characters.
+    - The second section lists regions in the form `WxH: c0 c1 c2 ...`,
+      where each `ci` is the count of presents of shape i to place.
+
+    This implementation only uses the region dimensions and the counts
+    of presents to compute a required area per region and checks whether
+    the available area is sufficient.
+    """
+
+    def part1(self, data: str) -> int:
+        """Count how many regions can fit all of their requested presents.
+
+        The raw input is split on blank lines. All blocks except the last
+        are interpreted as shape definitions; the final block contains the
+        region lines. For each region line of the form:
+
+            WxH: n0 n1 n2 ...
+
+        it computes a required area of `8 * sum(ni)` and compares it to
+        `width * height`. If the region has at least this much area, it
+        is counted as able to fit all presents.
+
+        Args:
+            data: Full puzzle input as a single string.
+
+        Returns
+        -------
+            int: Number of regions that can fit all of their listed presents.
+        """
+        *shape_blocks, regions = data.split("\n\n")
+
+        shapes: list[str] = []
+        for block in shape_blocks:
+            lines = block.split("\n")
+            body = "\n".join(lines[1:])
+            shapes.append(body)
+
+        count = 0
+        for region in regions.split("\n"):
+            region = region.strip()
+            if not region:
+                continue
+
+            width, height, *nums = map(int, region.replace("x", " ").replace(":", "").split())
+            required = 8 * sum(nums)
+            if width * height >= required:
+                count += 1
+
+        return count
+
+    def part2(self, data: str) -> str:
+        """Return a festive message after evaluating all regions.
+
+        Part 2 of this solution does not perform additional computation
+        on the input; instead, it simply returns a celebratory string to
+        mark the completion of the Advent of Code event.
+
+        Args:
+            data: Full puzzle input as a single string.
+
+        Returns
+        -------
+            str: Festive completion message.
+        """
+        return "Merry Christmas!"

_2025/tests/data/day12/test_01_input.txt

@@ -0,0 +1,33 @@
+0:
+###
+##.
+##.
+
+1:
+###
+##.
+.##
+
+2:
+.##
+###
+##.
+
+3:
+##.
+###
+##.
+
+4:
+###
+#..
+###
+
+5:
+###
+.#.
+###
+
+4x4: 0 0 0 0 2 0
+12x5: 1 0 1 0 2 2
+12x5: 1 0 1 0 3 2

_2025/tests/test_12.py

@@ -0,0 +1,25 @@
+"""Test suite for Day 12: Christmas Tree Farm
+
+This module contains tests for the Day 12 solution, which checks for
+each rectangular region under a Christmas tree whether it can fit all
+requested oddly-shaped presents. The tests verify:
+
+1. Part 1: Counting how many regions can fit their listed presents
+"""
+
+from aoc.models.tester import TestSolutionUtility
+
+
+def test_day12_part1() -> None:
+    """Test counting regions that can fit all presents.
+
+    This test runs the solution for Part 1 of the puzzle against the
+    provided test input and compares the result with the expected output.
+    """
+    TestSolutionUtility.run_test(
+        year=2025,
+        day=12,
+        is_raw=True,
+        part_num=1,
+        expected=3,
+    )