advent-of-code/src/holt59/aoc/2024/day8.py

import itertools as it
from collections import defaultdict
from typing import Any, Iterator, cast

from ..base import BaseSolver


def compute_antinodes(
    a1: tuple[int, int],
    a2: tuple[int, int],
    n_rows: int,
    n_cols: int,
    min_distance: int = 1,
    max_distance: int | None = 1,
):
    if a1[0] > a2[0]:
        a1, a2 = a2, a1

    d_row, d_col = a2[0] - a1[0], a2[1] - a1[1]

    points: list[tuple[int, int]] = []

    for c in range(min_distance, (max_distance or n_rows) + 1):
        row_1, col_1 = a1[0] - c * d_row, a1[1] - c * d_col
        row_2, col_2 = a2[0] + c * d_row, a2[1] + c * d_col

        valid_1, valid_2 = (
            0 <= row_1 < n_rows and 0 <= col_1 < n_cols,
            0 <= row_2 < n_rows and 0 <= col_2 < n_cols,
        )

        if not valid_1 and not valid_2:
            break

        if valid_1:
            points.append((row_1, col_1))
        if valid_2:
            points.append((row_2, col_2))

    return tuple(points)


class Solver(BaseSolver):
    def solve(self, input: str) -> Iterator[Any]:
        lines = input.splitlines()

        n_rows, n_cols = len(lines), len(lines[0])

        antennas: dict[str, list[tuple[int, int]]] = defaultdict(list)
        for i, j in it.product(range(n_rows), range(n_cols)):
            if lines[i][j] != ".":
                antennas[lines[i][j]].append((i, j))

        yield len(
            cast(set[tuple[int, int]], set()).union(
                it.chain(
                    *(
                        compute_antinodes(a1, a2, n_rows, n_cols)
                        for antennas_of_frequency in antennas.values()
                        for a1, a2 in it.permutations(antennas_of_frequency, 2)
                    )
                )
            )
        )

        yield len(
            cast(set[tuple[int, int]], set()).union(
                it.chain(
                    *(
                        compute_antinodes(a1, a2, n_rows, n_cols, 0, None)
                        for antennas_of_frequency in antennas.values()
                        for a1, a2 in it.permutations(antennas_of_frequency, 2)
                    )
                )
            )
        )