Merge pull request #97 from wimglenn/2023/11

day 11

aoc_wim/aoc2023/q11.py

@@ -0,0 +1,36 @@
+"""
+--- Day 11: Cosmic Expansion ---
+https://adventofcode.com/2023/day/11
+"""
+from aocd import data
+from itertools import combinations
+from aoc_wim.zgrid import ZGrid
+from aoc_wim.zgrid import manhattan_distance
+
+grid = ZGrid(data)
+h, w = grid.height, grid.width
+gs = grid.z("#", first=False)
+g_cols = {g.real for g in gs}
+g_rows = {g.imag for g in gs}
+empty_cols = [i for i in range(w) if i not in g_cols]
+empty_rows = [i for i in range(h) if i not in g_rows]
+
+# expansion factor for part b
+f = 1_000_000
+if len(gs) == 9:
+    # 9 galaxies for the example data
+    # use a smaller expansion factor
+    f = 100
+
+a = b = 0
+for g0, g1 in combinations(gs, 2):
+    d = manhattan_distance(g0, g1)
+    c01 = range(*sorted([int(g0.real), int(g1.real)]))
+    r01 = range(*sorted([int(g0.imag), int(g1.imag)]))
+    c = sum(1 for c in empty_cols if c in c01)
+    r = sum(1 for r in empty_rows if r in r01)
+    a += d + c + r
+    b += d + (c + r) * (f - 1)
+
+print("answer_a:", a)
+print("answer_b:", b)

tests/2023/11/0.txt

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+...#......
+.......#..
+#.........
+..........
+......#...
+.#........
+.........#
+..........
+.......#..
+#...#.....
+374
+8410  # expansion factor 100