Solve 2018 day 18

2018/d18.py

@@ -0,0 +1,68 @@
+from lib import get_data, Grid2D
+from copy import deepcopy
+
+
+def part_2(data, target=10):
+    g = Grid2D(data)
+    seen = {}
+    i = 0
+    while i < target:
+        ng = deepcopy(g)
+        for r in range(g.n_rows):
+            for c in range(g.n_cols):
+                if g[(r, c)] == ".":
+                    tree_count = sum(
+                        [1 if g[nb] == "|" else 0 for nb in g.neighbors_adj((r, c))]
+                    )
+                    if tree_count >= 3:
+                        ng[(r, c)] = "|"
+                elif g[(r, c)] == "|":
+                    lumber_count = sum(
+                        [1 if g[nb] == "#" else 0 for nb in g.neighbors_adj((r, c))]
+                    )
+                    if lumber_count >= 3:
+                        ng[(r, c)] = "#"
+                elif g[(r, c)] == "#":
+                    tree_count = sum(
+                        [1 if g[nb] == "|" else 0 for nb in g.neighbors_adj((r, c))]
+                    )
+                    lumber_count = sum(
+                        [1 if g[nb] == "#" else 0 for nb in g.neighbors_adj((r, c))]
+                    )
+                    if tree_count > 0 and lumber_count > 0:
+                        pass
+                    else:
+                        ng[(r, c)] = "."
+                else:
+                    assert False
+
+        h = ng.hash()
+        if h in seen:
+            delta = i - seen[h]
+            while (i + delta) < target:
+                i += delta
+            seen = {}
+        else:
+            seen[h] = i
+        i += 1
+        g = ng
+
+    w = 0
+    l = 0
+    for r in range(g.n_rows):
+        for c in range(g.n_cols):
+            if g[(r, c)] == "|":
+                w += 1
+            elif g[(r, c)] == "#":
+                l += 1
+    print(l * w)
+
+
+def main():
+    data = get_data(__file__)
+    part_2(data, 10)
+    part_2(data, 1000000000)
+
+
+if __name__ == "__main__":
+    main()

README.md

@@ -106,7 +106,8 @@ written in Python.
 - Day 15: 185:11
 - Day 16: 36:10
 - Day 17: 180:00
-- Day 18:
+- Day 18: 24:04
+- Day 19: 
 
 # 2022
 

lib.py

@@ -56,6 +56,9 @@ class Grid2D:
         row, col = pos
         self.grid[row][col] = val
 
+    def hash(self):
+        return tuple(map(lambda row: tuple(row), self.grid))
+
     def clone_with_val(self, val):
         c = Grid2D("d\nd")
         c.n_rows = self.n_rows