Co-authored-by: Mikael CAPELLE <mikael.capelle@thalesaleniaspace.com> Co-authored-by: Mikaël Capelle <capelle.mikael@gmail.com> Reviewed-on: #3
123 lines
3.5 KiB
Python
123 lines
3.5 KiB
Python
import itertools as it
|
|
from typing import Any, Iterator, TypeAlias
|
|
|
|
from ..base import BaseSolver
|
|
|
|
NodeType: TypeAlias = tuple[tuple[int, int], tuple[int, int]]
|
|
EdgesType: TypeAlias = dict[NodeType, tuple[NodeType, set[tuple[int, int]]]]
|
|
|
|
ROTATE = {(-1, 0): (0, 1), (0, 1): (1, 0), (1, 0): (0, -1), (0, -1): (-1, 0)}
|
|
|
|
START_NODE: NodeType = ((-2, -2), (-1, 0))
|
|
FINAL_POS: tuple[int, int] = (-1, -1)
|
|
|
|
|
|
def move(
|
|
lines: list[str], pos: tuple[int, int], dir: tuple[int, int]
|
|
) -> tuple[tuple[int, int] | None, set[tuple[int, int]]]:
|
|
n_rows, n_cols = len(lines), len(lines[0])
|
|
row, col = pos
|
|
|
|
marked: set[tuple[int, int]] = set()
|
|
final_pos: tuple[int, int] | None = None
|
|
|
|
while True:
|
|
marked.add((row, col))
|
|
|
|
if not (0 <= row + dir[0] < n_rows and 0 <= col + dir[1] < n_cols):
|
|
final_pos = None
|
|
break
|
|
|
|
if lines[row + dir[0]][col + dir[1]] != ".":
|
|
final_pos = (row, col)
|
|
break
|
|
|
|
row += dir[0]
|
|
col += dir[1]
|
|
|
|
return final_pos, marked
|
|
|
|
|
|
def compute_graph(lines: list[str], start_node: NodeType):
|
|
n_rows, n_cols = len(lines), len(lines[0])
|
|
|
|
edges: EdgesType = {}
|
|
|
|
start_pos, start_dir = start_node
|
|
end_pos, marked = move(lines, start_pos, start_dir)
|
|
assert end_pos is not None
|
|
edges[START_NODE] = ((end_pos, start_dir), marked)
|
|
|
|
for row, col in it.product(range(n_rows), range(n_cols)):
|
|
if lines[row][col] != "#":
|
|
continue
|
|
|
|
for start_pos, start_dir in (
|
|
((row - 1, col), (1, 0)),
|
|
((row + 1, col), (-1, 0)),
|
|
((row, col - 1), (0, 1)),
|
|
((row, col + 1), (0, -1)),
|
|
):
|
|
if 0 <= start_pos[0] < n_rows and 0 <= start_pos[1] < n_cols:
|
|
end_pos, marked = move(lines, start_pos, ROTATE[start_dir])
|
|
|
|
edges[start_pos, start_dir] = (
|
|
(end_pos or FINAL_POS, ROTATE[start_dir]),
|
|
marked,
|
|
)
|
|
|
|
return edges
|
|
|
|
|
|
def is_loop(lines: list[str], edges: EdgesType, position: tuple[int, int]):
|
|
row, col = position
|
|
current_node = START_NODE
|
|
found: set[NodeType] = set()
|
|
|
|
while current_node[0] != FINAL_POS and current_node not in found:
|
|
found.add(current_node)
|
|
|
|
target_node, edge_marked = edges[current_node]
|
|
|
|
if (row, col) in edge_marked:
|
|
# need to break the edge
|
|
target_dir = target_node[1]
|
|
end_pos, _ = move(
|
|
lines, (row - target_dir[0], col - target_dir[1]), ROTATE[target_dir]
|
|
)
|
|
current_node = (end_pos or FINAL_POS, ROTATE[target_dir])
|
|
else:
|
|
current_node = target_node
|
|
|
|
return current_node in found
|
|
|
|
|
|
class Solver(BaseSolver):
|
|
def solve(self, input: str) -> Iterator[Any]:
|
|
# read lines
|
|
lines = input.splitlines()
|
|
|
|
# find and delete original position
|
|
start_pos = next(
|
|
(i, j)
|
|
for i, row in enumerate(lines)
|
|
for j, col in enumerate(row)
|
|
if col == "^"
|
|
)
|
|
lines[start_pos[0]] = lines[start_pos[0]].replace("^", ".")
|
|
|
|
# compute edges from the map
|
|
edges = compute_graph(lines, (start_pos, (-1, 0)))
|
|
|
|
# part 1
|
|
marked: set[tuple[int, int]] = set()
|
|
current_node = START_NODE
|
|
|
|
while current_node[0] != FINAL_POS:
|
|
current_node, current_marked = edges[current_node]
|
|
marked = marked.union(current_marked)
|
|
|
|
yield len(marked)
|
|
|
|
yield sum(is_loop(lines, edges, pos) for pos in marked if pos != start_pos)
|