diff --git a/AP-Jupyternotebook.ipynb b/AP-Jupyternotebook.ipynb
index 426549a1ca70eed8e6410595828fc74e60c1ac31..326e1a1076d7ca725bd557124f090ffcf55cab30 100644
--- a/AP-Jupyternotebook.ipynb
+++ b/AP-Jupyternotebook.ipynb
@@ -1768,19 +1768,14 @@
     "        super().__init__(verbose, collect_stats)\n",
     "        self.h = heuristic\n",
     "\n",
-    "    # -----------------------------------------------\n",
-    "    # Solve\n",
-    "    # -----------------------------------------------\n",
-    "\n",
-    "    # =====================================\n",
-    "    # Params:\n",
-    "    # actions -> list of grounded actions\n",
-    "    # state -> initial state of the problem file\n",
-    "    # goals -> tuple with (positive predicates, negative predicates) of the goal\n",
-    "    # =====================================\n",
-    "\n",
-    "    # Positive goals and negative goals in a tuple.\n",
+    "    # maybe I can use some kind of structure to control the level of the tree.\n",
+    "    # keep only the things that changed in next state.\n",
     "    def solve(self, actions, state, goals):\n",
+    "        \"\"\"\n",
+    "            actions: list of grounded actions\n",
+    "            state: initial state of the problem file\n",
+    "            goals: tuple with (positive predicates, negative predicates) of the goal\n",
+    "        \"\"\"\n",
     "        frontier = queue.PriorityQueue()\n",
     "        came_from = {}\n",
     "        cost_so_far = {}\n",
@@ -1811,6 +1806,7 @@
     "                ):\n",
     "                    new_state = apply(current_state, (action.add_effects, action.del_effects))\n",
     "                    # +1 because this is the cost to move from one state to another.\n",
+    "                    # When not used, the result is the same.\n",
     "                    cost = cost_so_far[current_state] + 1\n",
     "                    if new_state not in cost_so_far or cost < cost_so_far[new_state]:\n",
     "                        cost_so_far[new_state] = cost\n",
@@ -1967,10 +1963,13 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 8,
    "metadata": {
+    "ExecuteTime": {
+     "end_time": "2020-05-16T18:10:58.555811Z",
+     "start_time": "2020-05-16T18:10:48.913387Z"
+    },
     "deletable": false,
-    "editable": false,
     "nbgrader": {
      "cell_type": "code",
      "checksum": "c07eca3f711fd6ebae434c43df578f51",
@@ -1982,9 +1981,18 @@
      "solution": false
     }
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Elapsed time: 9.634910106658936 Passed!\n",
+      "Elapsed time: 0 Passed!\n"
+     ]
+    }
+   ],
    "source": [
-    "#Student_tests\n",
+    "# Reset to non-editable.\n",
     "dwr = \"examples/dwr/dwr.pddl\"\n",
     "pb1 = \"examples/dwr/pb1.pddl\"\n",
     "pb2 = \"examples/dwr/pb2.pddl\"\n",
@@ -1994,7 +2002,7 @@
     "print(\"Elapsed time:\", str(time) + (\" Passed!\" if time <= 60.0 else \" Timeout!\"))\n",
     "\n",
     "plan, time = planner.solve_file(dwr, pb2)\n",
-    "print(\"Elapsed time:\", str(time) + (\" Passed!\" if time <= 60.0 else \" Timeout!\"))\n"
+    "print(\"Elapsed time:\", str(time) + (\" Passed!\" if time <= 60.0 else \" Timeout!\"))"
    ]
   },
   {