2023 day 11.

2023/day10.py

@@ -68,7 +68,7 @@ mapping: dict[tuple[int, int], dict[tuple[int, int], Symbol]] = {
 lines[si][sj] = mapping[di1, dj1][di2, dj2]
 
 # find the points inside the loop using an adaptation of ray casting for a discrete
-# grid (https://en.wikipedia.org/wiki/Ray_casting)
+# grid (https://stackoverflow.com/a/218081/2666289)
 #
 # use a set for faster '... in loop' check
 #

2023/day11.py

@@ -1,13 +1,41 @@
 import sys
-from collections import defaultdict
-from dataclasses import dataclass
+
+import numpy as np
 
 lines = sys.stdin.read().splitlines()
 
+data = np.array([[c == "#" for c in line] for line in lines])
+
+rows = {c for c in range(data.shape[0]) if not data[c, :].any()}
+columns = {c for c in range(data.shape[1]) if not data[:, c].any()}
+
+galaxies_y, galaxies_x = np.where(data)  # type: ignore
+
+
+def compute_total_distance(expansion: int) -> int:
+    distances: list[int] = []
+    for g1 in range(len(galaxies_y)):
+        x1, y1 = int(galaxies_x[g1]), int(galaxies_y[g1])
+        for g2 in range(g1 + 1, len(galaxies_y)):
+            x2, y2 = int(galaxies_x[g2]), int(galaxies_y[g2])
+
+            dx = sum(
+                1 + (expansion - 1) * (x in columns)
+                for x in range(min(x1, x2), max(x1, x2))
+            )
+            dy = sum(
+                1 + (expansion - 1) * (y in rows)
+                for y in range(min(y1, y2), max(y1, y2))
+            )
+
+            distances.append(dx + dy)
+    return sum(distances)
+
+
 # part 1
-answer_1 = ...
+answer_1 = compute_total_distance(2)
 print(f"answer 1 is {answer_1}")
 
 # part 2
-answer_2 = ...
+answer_2 = compute_total_distance(1000000)
 print(f"answer 2 is {answer_2}")

2023/inputs/day11.txt

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2023/tests/day11.txt

@@ -0,0 +1,10 @@
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+.......#..
+#.........
+..........
+......#...
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+.........#
+..........
+.......#..
+#...#.....