Solve 2019 day 24

2019/24_bugs.py

@@ -0,0 +1,97 @@
+#!/usr/bin/env python3
+import sys
+from collections import defaultdict
+
+def read_grid(f):
+    lines = [line.replace('\n', '') for line in f]
+    return tuple(x == '#' for line in lines for x in line), len(lines[0])
+
+def evolve_simple(grid, w):
+    h = len(grid) // w
+
+    def adjacent(i):
+        y, x = divmod(i, w)
+        nb = 0
+        if x > 0:
+            nb += grid[i - 1]
+        if x < w - 1:
+            nb += grid[i + 1]
+        if y > 0:
+            nb += grid[i - w]
+        if y < h - 1:
+            nb += grid[i + w]
+        return nb
+
+    def die_or_infest(i, bug):
+        return adjacent(i) == 1 if bug else 1 <= adjacent(i) <= 2
+
+    return tuple(die_or_infest(i, bug) for i, bug in enumerate(grid))
+
+def find_recurring(grid, w):
+    seen = set()
+    while grid not in seen:
+        seen.add(grid)
+        grid = evolve_simple(grid, w)
+    return grid
+
+def biodiversity(grid):
+    return sum(bug << i for i, bug in enumerate(grid))
+
+def evolve_infinite(grid, w, minutes):
+    l = len(grid)
+    assert l == w * w
+    mid = w // 2 * w + w // 2
+
+    top_edge = tuple(range(w))
+    bottom_edge = tuple(range(l - w, l))
+    left_edge = tuple(range(0, l, w))
+    right_edge = tuple(range(w - 1, l, w))
+
+    def spread(x, y, nx, ny, level):
+        ni = ny * w + nx
+        if ni == mid:
+            if x > nx:
+                return right_edge, level + 1
+            elif x < nx:
+                return left_edge, level + 1
+            elif y > ny:
+                return bottom_edge, level + 1
+            elif y < ny:
+                return top_edge, level + 1
+        elif nx == -1:
+            return (mid - 1,), level - 1
+        elif nx == w:
+            return (mid + 1,), level - 1
+        elif ny == -1:
+            return (mid - w,), level - 1
+        elif ny == w:
+            return (mid + w,), level - 1
+        else:
+            return (ni,), level
+
+    def neighbors(i, level):
+        y, x = divmod(i, w)
+        yield spread(x, y, x - 1, y, level)
+        yield spread(x, y, x + 1, y, level)
+        yield spread(x, y, x, y - 1, level)
+        yield spread(x, y, x, y + 1, level)
+
+    def evolve(bugs):
+        adjacent = defaultdict(int)
+        for i, level in bugs:
+            y, x = divmod(i, w)
+            for nbs, nblev in neighbors(i, level):
+                for nb in nbs:
+                    adjacent[(nb, nblev)] += 1
+        return {x for x, a in adjacent.items()
+                if a == 1 or (a == 2 and x not in bugs)}
+
+    bugs = {(i, 0) for i, bug in enumerate(grid) if bug}
+    while minutes > 0:
+        bugs = evolve(bugs)
+        minutes -= 1
+    return len(bugs)
+
+grid, w = read_grid(sys.stdin)
+print(biodiversity(find_recurring(grid, w)))
+print(evolve_infinite(grid, w, 200))

2019/input/24

@@ -0,0 +1,5 @@
+##.#.
+#..#.
+.....
+....#
+#.###