Implement 2024 day 14

Author: bertptrs

2024/src/aoc/days/day14.py

@@ -0,0 +1,73 @@
+import itertools
+import math
+import re
+
+import numpy
+
+from . import SeparateRunner
+
+NASTY_REGEX = re.compile(r"p=(-?\d+),(-?\d+) v=(-?\d+),(-?\d+)")
+
+
+class DayRunner(SeparateRunner):
+    @classmethod
+    def part1(cls, input: str, width: int = 101, height: int = 103) -> int:
+        points = NASTY_REGEX.findall(input)
+
+        quadrants = [0] * 4
+
+        x_middle = width // 2
+        y_middle = height // 2
+
+        for point in points:
+            x, y, dx, dy = map(int, point)
+
+            rx = ((x + dx * 100) % width + width) % width
+            ry = ((y + dy * 100) % height + height) % height
+
+            match rx:
+                case _ if rx < x_middle:
+                    xq = 0
+                case _ if rx > x_middle:
+                    xq = 1
+                case _:
+                    continue
+
+            match ry:
+                case _ if ry < y_middle:
+                    yq = 0
+                case _ if ry > y_middle:
+                    yq = 1
+                case _:
+                    continue
+
+            quadrants[2 * yq + xq] += 1
+
+        return math.prod(quadrants)
+
+    @classmethod
+    def part2(cls, input: str) -> int:
+        width = 101
+        height = 103
+
+        points = NASTY_REGEX.findall(input)
+        points_fast = numpy.array([list(map(int, point)) for point in points])
+
+        positions = points_fast[:, 0:2]
+        velocities = points_fast[:, 2:]
+
+        target = len(velocities)
+
+        # Assumption: when the easter egg happens, no robots overlap, and this is the
+        # only time this happens. There is no reason this should work but it does.
+        mod_base = numpy.array([width, height])
+        for i in itertools.count(1):
+            positions += velocities
+
+            positions %= mod_base
+            positions += mod_base
+            positions %= mod_base
+
+            if len(numpy.unique(positions, axis=0)) == target:
+                # TODO: print the Christmas tree, Eric prepared it for us so nicely
+                return i

2024/tests/samples/14.txt

@@ -0,0 +1,12 @@
+p=0,4 v=3,-3
+p=6,3 v=-1,-3
+p=10,3 v=-1,2
+p=2,0 v=2,-1
+p=0,0 v=1,3
+p=3,0 v=-2,-2
+p=7,6 v=-1,-3
+p=3,0 v=-1,-2
+p=9,3 v=2,3
+p=7,3 v=-1,2
+p=2,4 v=2,-3
+p=9,5 v=-3,-3

2024/tests/test_day14.py

@@ -0,0 +1,7 @@
+from aoc.days.day14 import DayRunner
+
+from . import get_data
+
+
+def test_sample_part1() -> None:
+    assert DayRunner.part1(get_data(14), width=11, height=7) == 12