2024 day 8.

src/holt59/aoc/2024/day8.py

@@ -1,7 +1,76 @@
-from typing import Any, Iterator
+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]: ...
+    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)
+                    )
+                )
+            )
+        )

src/holt59/aoc/inputs/holt59/2024/day8.txt

@@ -0,0 +1,50 @@
+.........................p........................
+......................h....C............M.........
+..............................p....U..............
+..5..................p............................
+..6z...........................................C..
+...............c...........zV.....................
+...5.....c........................................
+.Z.............h........S...z....9................
+.O............................9...z........M..C...
+..O....5..............................F..M..C.....
+..Z.........5.c...............M....V..............
+........ZO................q.......................
+s...O................h..Uq.....7V...........4.....
+.q.g..............c.............p.......4.........
+............hZ.............................4G.....
+6s...........................U.Q.....3............
+.......6.................9.......Q.............3..
+....s..D.........................6................
+.............................................FL...
+..................................................
+..g...D.........q.....f.......Q...F....L......7...
+...............2.........f.............V.L...4....
+...................2.s...................f3......G
+....g...........................v......7P.........
+..2..g.............d.....v...........P.......1....
+..............u.........f.............L........G..
+.........l.D....u...............d........o..P.....
+..................8...............9..1......o...7.
+............l.....................................
+...................l...S...........F.......o..U...
+.......................u...S......................
+..........l....u...............m...........P....G.
+......................................1.8.......o.
+..................................................
+..................v.......S................0......
+.............v........d.....1.....................
+..................................................
+..........D....................................0..
+...................m.............H..........0.....
+...................................d......0.......
+..................................................
+....Q.............................................
+................................H.................
+........................H....................8....
+..................................................
+..................................................
+.........................................8........
+.......................H3.........................
+............................m.....................
+................................m.................

src/holt59/aoc/inputs/tests/2024/day8.txt

@@ -0,0 +1,12 @@
+............
+........0...
+.....0......
+.......0....
+....0.......
+......A.....
+............
+............
+........A...
+.........A..
+............
+............