2024: day 8. part 1. python

Author: Tsovak

src/2024/day08/1/data.txt

@@ -0,0 +1,50 @@
+...............e.........................i........
+...............................1.......i.0........
+..............................s.0......d..........
+........................i....B.I............d.....
+.............................s....................
+................J.................................
+.....................L.....0i.......4...d.........
+.N...e...........................s..R.....4.....I.
+........e.........v................1......R....I..
+.............G..............0.....1...............
+..2...N.............B......................4...R..
+..............2...................N..........4s...
+..p...................................1..b..I.....
+..................p...........B........b...R......
+....................................b.............
+........W.......C.....w...........................
+............7....u.............B..................
+...W.................u......................bw....
+.......p.2...........v......................9.....
+.E.....C....u................................9....
+E....Y................u.D........9...........J....
+.......2..........................................
+............................J.................c...
+.............7...K..D..............J..............
+.....C.Wq........t.................T..............
+............Yt......v.............................
+..W......................3...............w........
+..7.....j................T...D.....n......8.....c.
+.........E...............nTD......................
+...r....E..........Y............n.......P........c
+......K........G......L...........................
+......................G.....L....v................
+..............G...t......q.............l.8........
+......................q............l..............
+...6........r.............................w..c....
+..6.........3.......Qk........T...................
+......Y...............j.................n.........
+..K.....S.....r......j.....U......9.l......8......
+........................U......................P..
+.....................q............................
+.......K......5..N.....j.7.Q......................
+...................p..k...U..........L.Q..........
+.r......3...S.......k........y....8U....Q.......P.
+.......S....g..3..................................
+.....S..........gk................................
+................5...................yP............
+.......................g......yV..l...............
+.........6.5...............V......................
+..................6..5..V.........................
+.............g.......................y..........V.

src/2024/day08/1/solution.py

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+import os
+from itertools import product
+
+
+def read_lines() -> list[str]:
+    filename = os.path.join(os.path.dirname(os.path.abspath(__file__)), 'data.txt')
+    with open(filename, "rb") as f:
+        return [line.decode("utf-8").strip() for line in f.readlines()]
+
+
+lines = read_lines()
+matrix = [list(line) for line in lines]
+
+
+def is_within_bounds(point, bounds):
+    return 0 <= point[0] < bounds[0] and 0 <= point[1] < bounds[1]
+
+
+def find_antinodes(matrix):
+    height, width = len(matrix), len(matrix[0])
+    antennas = {}
+
+    # antennas by frequency
+    for y, x in product(range(height), range(width)):
+        if matrix[y][x] != '.':
+            antennas.setdefault(matrix[y][x], []).append((x, y))
+
+    antinodes = set()
+
+    for _, antenna_list in antennas.items():
+        for i, (x1, y1) in enumerate(antenna_list):
+            for (x2, y2) in antenna_list[i + 1:]:
+                x_diff, y_diff = x2 - x1, y2 - y1
+
+                # calculate symmetrical antinodes
+                outside_a = (x1 - x_diff, y1 - y_diff)
+                outside_b = (x2 + x_diff, y2 + y_diff)
+
+                if is_within_bounds(outside_a, (width, height)):
+                    antinodes.add(outside_a)
+                if is_within_bounds(outside_b, (width, height)):
+                    antinodes.add(outside_b)
+
+    return len(antinodes)
+
+
+result = find_antinodes(matrix)
+print(result)