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day16.py
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day16.py
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from .solver import Solver
def _trace_beam(data: list[str], initial_beam_head: tuple[int, int, int, int]):
wx = len(data[0])
wy = len(data)
beam_heads = [initial_beam_head]
seen_beam_heads = set()
while beam_heads:
next_beam_heads = []
for x, y, dx, dy in beam_heads:
seen_beam_heads.add((x, y, dx, dy))
nx, ny = (x + dx), (y + dy)
if nx < 0 or nx >= wx or ny < 0 or ny >= wy:
continue
obj = data[ny][nx]
if obj == '|' and dx != 0:
next_beam_heads.append((nx, ny, 0, 1))
next_beam_heads.append((nx, ny, 0, -1))
elif obj == '-' and dy != 0:
next_beam_heads.append((nx, ny, 1, 0))
next_beam_heads.append((nx, ny, -1, 0))
elif obj == '/':
next_beam_heads.append((nx, ny, -dy, -dx))
elif obj == '\\':
next_beam_heads.append((nx, ny, dy, dx))
else:
next_beam_heads.append((nx, ny, dx, dy))
beam_heads = [x for x in next_beam_heads if x not in seen_beam_heads]
energized = {(x, y) for x, y, _, _ in seen_beam_heads}
return len(energized) - 1
class Day16(Solver):
def __init__(self):
super().__init__(16)
def presolve(self, input: str):
data = input.splitlines()
self.possible_energized_cells = (
[_trace_beam(data, (-1, y, 1, 0)) for y in range(len(data))] +
[_trace_beam(data, (x, -1, 0, 1)) for x in range(len(data[0]))] +
[_trace_beam(data, (len(data[0]), y, -1, 0)) for y in range(len(data))] +
[_trace_beam(data, (x, len(data), 0, -1)) for x in range(len(data[0]))])
def solve_first_star(self) -> int:
return self.possible_energized_cells[0]
def solve_second_star(self) -> int:
return max(self.possible_energized_cells)
# vim: ts=2:sw=2:et