Solve 2021 day 20, 21, 23, 25

lib.py

@@ -59,6 +59,10 @@ class Grid2D:
     def hash(self):
         return tuple(map(lambda row: tuple(row), self.grid))
 
+    def clone(self):
+        from copy import deepcopy
+        return deepcopy(self)
+
     def clone_with_val(self, val):
         c = Grid2D("d\nd")
         c.n_rows = self.n_rows