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AoC 2024 day 14 part 2
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@loociano
loociano committed Dec 14, 2024
1 parent 8b2136d commit 815068e
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52 changes: 48 additions & 4 deletions aoc2024/src/day14/python/solution.py
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,9 @@ def __init__(self, position: Position, velocity: Velocity, world_size: WorldSize
self._width = world_size[0]
self._height = world_size[1]

def position(self) -> Position:
return self._x, self._y

def move(self) -> None:
"""Moves robot from its position according to its constant velocity."""
self._x += self._dx
Expand Down Expand Up @@ -74,14 +77,55 @@ def _parse(input: Sequence[str], world_size: WorldSize) -> tuple[Robot, ...]:
return tuple(robots)


def _simulate(robots: tuple[Robot, ...], elapsed_seconds):
for _ in range(elapsed_seconds):
for robot in robots:
robot.move()


def _calc_safety_factor(robots: tuple[Robot, ...]) -> int:
quadrant_counts = Counter(map(lambda r: r.get_quadrant(), robots))
# Assumes there will be at least one robot per quadrant.
return math.prod(quadrant_counts.get(quadrant_num) for quadrant_num in range(1, 5))


def get_safety_factor(input: Sequence[str], world_size: WorldSize = _DEFAULT_SIZE,
elapsed_seconds: int = 0) -> int:
"""Returns safety factor as the multiplication of robots per quadrant after a number of seconds.
Robots that end up between quadrants do not count towards safety factor."""
robots = _parse(input, world_size)
for _ in range(elapsed_seconds):
_simulate(robots, elapsed_seconds)
return _calc_safety_factor(robots)


def _print_world(robots: tuple[Robot, ...], world_size: WorldSize) -> None:
counter = Counter(map(lambda r: r.position(), robots))
for y in range(world_size[1]):
line = []
for x in range(world_size[0]):
line.append('X' if counter.get((x, y)) is not None else '.')
print(''.join(line))


def get_seconds_to_easter_egg(input: Sequence[str], world_size: WorldSize = _DEFAULT_SIZE,
elapsed_seconds: int = 0) -> int:
"""Returns number of seconds that must elapse to display an Easter egg.
The Easter egg is a picture of a Christmas tree.
"""
robots = _parse(input, world_size)
min_safety_factor = math.inf
result = 0
for t in range(1, elapsed_seconds + 1):
for robot in robots:
robot.move()
quadrant_counts = Counter(map(lambda r: r.get_quadrant(), robots))
# Assumes there will be at least one robot per quadrant.
return math.prod(quadrant_counts.get(quadrant_num) for quadrant_num in range(1, 5))
safety_factor = _calc_safety_factor(robots)
# Thanks to reddit.com/r/adventofcode we know that the picture is small and
# fits in one quadrant. In other words, it's when the safest factor is the
# lowest.
if safety_factor < min_safety_factor:
min_safety_factor = safety_factor
result = t
# Only print state when finding a lower safety factor.
print(f't={t}')
_print_world(robots, world_size)
return result
111 changes: 110 additions & 1 deletion aoc2024/test/day14/python/test_solution.py
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Expand Up @@ -14,7 +14,7 @@
import unittest

from common.python3.AdventOfCodeTestCase import AdventOfCodeTestCase
from aoc2024.src.day14.python.solution import get_safety_factor
from aoc2024.src.day14.python.solution import get_safety_factor, get_seconds_to_easter_egg


class TestSolution(AdventOfCodeTestCase):
Expand All @@ -29,6 +29,115 @@ def test_part1_withExample_correct(self):
def test_part1_withPuzzleInput_correct(self):
self.assertEqual(215987200, get_safety_factor(self.input, elapsed_seconds=100))

def test_part2_withPuzzleInput_correct(self):
self.assertEqual(8050, get_seconds_to_easter_egg(self.input, elapsed_seconds=10000))
"""
t=8050
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"""


if __name__ == '__main__':
unittest.main()

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