Solve day 8

2024/08_antinodes.py

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+#!/usr/bin/env python3
+import sys
+from functools import partial
+from itertools import chain, permutations, starmap
+
+def parse(f):
+    antennas = {}
+    for y, line in enumerate(f):
+        for x, char in enumerate(line[:-1]):
+            if char != '.':
+                antennas.setdefault(char, []).append((x, y))
+    return antennas, x + 1, y + 1
+
+def subtract_pairs(antennas):
+    for locs in antennas.values():
+        for (xa, ya), (xb, yb) in permutations(locs, 2):
+            yield xb, yb, xb - xa, yb - ya
+
+def antinodes1(w, h, x, y, dx, dy):
+    if 0 <= x + dx < w and 0 <= y + dy < h:
+        yield x + dx, y + dy
+
+def antinodes2(w, h, x, y, dx, dy):
+    while 0 <= x < w and 0 <= y < h:
+        yield x, y
+        x += dx
+        y += dy
+
+antennas, w, h = parse(sys.stdin)
+pairs = list(subtract_pairs(antennas))
+print(len(set(chain.from_iterable(starmap(partial(antinodes1, w, h), pairs)))))
+print(len(set(chain.from_iterable(starmap(partial(antinodes2, w, h), pairs)))))

2024/input/8

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+..E...............3.....m......d.i................
+............f.3.......C....d........A.............
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+..z.........D..........G.g........................
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+.........I..c.nr...............M................O.
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