Add solution to 2024-12-08

Author: fuglede

2024/day08/solutions.py

@@ -0,0 +1,28 @@
+from collections import defaultdict
+from itertools import count, permutations
+
+with open("input") as f:
+    ls = f.read().strip().split("\n")
+
+board = {i + 1j * j: x for i, l in enumerate(ls) for j, x in enumerate(l)}
+antennas = defaultdict(list)
+for z, x in board.items():
+    if x not in (".", "#"):
+        antennas[x].append(z)
+
+# Part 1
+antinodes = {
+    2 * z2 - z1 for zs in antennas.values() for z1, z2 in permutations(zs, 2)
+} & board.keys()
+print(len(antinodes))
+
+# Part 2
+antinodes = set()
+for zs in antennas.values():
+    for z1, z2 in permutations(zs, 2):
+        for i in count():
+            z = z2 + i * (z2 - z1)
+            if z not in board:
+                break
+            antinodes.add(z)
+print(len(antinodes))