Solve 2019 day 24

2019/d24.py

@@ -0,0 +1,107 @@
+from lib import get_data, Grid2D, add2
+from collections import defaultdict
+
+
+data = get_data(__file__)
+
+g = Grid2D(data)
+seen = set()
+while True:
+    h = g.hash()
+    if h in seen:
+        break
+    else:
+        seen.add(h)
+
+    gn = g.clone_with_val(".")
+    for r in range(g.n_rows):
+        for c in range(g.n_cols):
+            p = (r, c)
+            nb_bugs = sum(1 for nb in g.neighbors_ort(p) if g[nb] == "#")
+            if g[p] == "#" and nb_bugs == 1:
+                gn[p] = "#"
+            if g[p] == "." and nb_bugs in [1, 2]:
+                gn[p] = "#"
+    g = gn
+
+
+t = 0
+p = 1
+for r in range(g.n_rows):
+    for c in range(g.n_cols):
+        if g[(r, c)] == "#":
+            t += p
+        p *= 2
+print(t)
+
+N = (-1, 0)
+E = (0, 1)
+S = (1, 0)
+W = (0, -1)
+DIRS = [N, E, S, W]
+ROW, COL = 0, 1
+
+# data = get_data(__file__)
+g = Grid2D(data)
+bugs = [(0, r, c) for (r, c) in g.find("#")]
+middle = (g.n_rows // 2, g.n_cols // 2)
+rows, cols = g.n_rows, g.n_cols
+
+
+def get_edge(side):
+    edges = {
+        S: [(0, c) for c in range(cols)],
+        N: [(rows - 1, c) for c in range(cols)],
+        W: [(r, cols - 1) for r in range(rows)],
+        E: [(r, 0) for r in range(rows)],
+    }
+    return edges[side]
+
+
+def get_neighbors(pos):
+    level, row, col = pos
+    neighbors = []
+
+    for d in DIRS:
+        nb = add2((row, col), d)
+        if nb == middle:
+            for ir, ic in get_edge(d):
+                neighbors.append((level - 1, ir, ic))
+        elif nb[ROW] in {-1, rows} or nb[COL] in {-1, cols}:
+            nr, nc = nb
+            if nr == -1:
+                neighbors.append((level + 1, *add2(middle, N)))
+            if nr == rows:
+                neighbors.append((level + 1, *add2(middle, S)))
+            if nc == -1:
+                neighbors.append((level + 1, *add2(middle, W)))
+            if nc == cols:
+                neighbors.append((level + 1, *add2(middle, E)))
+        else:
+            nr, nc = nb
+            neighbors.append((level, nr, nc))
+    return neighbors
+
+
+assert len(get_neighbors((0, 1, 1))) == 4
+assert len(get_neighbors((0, 3, 3))) == 4
+assert len(get_neighbors((0, 0, 3))) == 4
+assert len(get_neighbors((0, 0, 4))) == 4
+assert len(get_neighbors((0, 2, 3))) == 8
+
+for _ in range(200):
+    neighbors = defaultdict(int)
+    current_bugs = set(bugs)
+    for pos in bugs:
+        for nb in get_neighbors(pos):
+            neighbors[nb] += 1
+
+    new_bugs = []
+    for pos, count in neighbors.items():
+        if pos in current_bugs and count == 1:
+            new_bugs.append(pos)
+        if pos not in current_bugs and count in [1, 2]:
+            new_bugs.append(pos)
+    bugs = new_bugs
+
+print(len(bugs))