Day 11

day11/day11.py

@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+
+import sys
+
+from utils import io
+from utils.grid import Grid
+from utils.math import manhattan_dist
+
+
+def rot_90(lst):
+    return ["".join(list(reversed(x))) for x in zip(*lst)]
+
+
+def parse(lines, padding=2):
+    verticals = []
+    for i in range(len(lines) - 1):
+        verticals.append(lines[i])
+        if set(list(lines[i])) == {"."}:
+            for _ in range(0, padding - 1):
+                verticals.append(lines[i])
+    verticals.append(lines[-1])
+
+    lines = rot_90(verticals)
+    horizontals = []
+    for i in range(len(lines) - 1):
+        horizontals.append(lines[i])
+        if set(list(lines[i])) == {"."}:
+            for _ in range(0, padding - 1):
+                horizontals.append(lines[i])
+    horizontals.append(lines[-1])
+    lines = rot_90(rot_90(rot_90(horizontals)))
+
+    grid = Grid.from_lines(lines)
+
+    galaxies = set()
+
+    def visitor(_, pos, val):
+        if val == "#":
+            galaxies.add(pos)
+
+    grid.walk(visitor)
+
+    return grid, galaxies
+
+
+def solve(filename, padding=2):
+    _, galaxies = parse(io.get_lines(filename), padding)
+
+    sum = 0
+    galaxies = list(galaxies)
+    for i in range(0, len(galaxies)):
+        for j in range(i + 1, len(galaxies)):
+            sum += manhattan_dist(galaxies[i][0], galaxies[i][1], galaxies[j][0], galaxies[j][1])
+
+    return sum
+
+
+def main():
+    assert solve("example.txt") == 374
+    assert solve("example.txt") == 374
+    assert solve("example.txt", 10) == 1030
+    print(solve("../input/2023/day11.txt"))  # = 9565386
+
+    # part 2
+    # solve("example.txt", 20)  # = 1850 => 1850 - 1030 = 820
+    # solve("example.txt", 30)  # = 2670 => 2670 - 1850 = 820
+    # solve("example.txt", 40)  # = 3490 => 3490 - 2670 = 820
+    # solve("example.txt", 50)  # = 4310 => 4310 - 3490 = 820
+    # so example scales with 820 per 10
+    # example2 with 100:
+    # 90 / 10 = 9
+    # 9 * 820 = 7380
+    # 7380 + 1030 = 8410
+
+    # lets just do the math
+    # print(solve("../input/2023/day11.txt"))     # = 9565386
+    # print(solve("../input/2023/day11.txt", 3))  # = 10423365
+    # print(solve("../input/2023/day11.txt", 10)) # = 16429218
+    # print(solve("../input/2023/day11.txt", 15)) # = 20719113
+    # increases linearly after a while, let's try 20
+    g1 = 20
+    g2 = 30
+    s1 = solve("../input/2023/day11.txt", g1)  # = 25009008
+    s2 = solve("../input/2023/day11.txt", g2)  # = 33588798
+    print(((1000000 - g2) // (g2 - g1)) * (s2 - s1) + s2)
+
+
+if __name__ == "__main__":
+    sys.exit(main())

day11/example.txt

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+...#......
+.......#..
+#.........
+..........
+......#...
+.#........
+.........#
+..........
+.......#..
+#...#.....

test/math.py

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+import unittest
+
+from utils.math import manhattan_dist, sign
+
+
+class TestMath(unittest.TestCase):
+    def test_sign(self):
+        self.assertEqual(-1, sign(-4))
+        self.assertEqual(1, sign(8))
+        self.assertEqual(0, sign(0))
+
+    def test_manhattan_dist(self):
+        self.assertEqual(1 + 10, manhattan_dist(0, 4, -10, 3))
+
+
+if __name__ == "__main__":
+    unittest.main()

utils/math.py

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+def manhattan_dist(x1, y1, x2, y2):
+    return abs(x2 - x1) + abs(y2 - y1)
+
+
+def sign(a):
+    return (a > 0) - (a < 0)