Added three state variable visit_state which will be useful for more advanced challenges such as topological sort.

graphs_trees/graph/graph.py

@@ -1,11 +1,18 @@
 from collections import OrderedDict
+from enum import Enum  # Python 2 users: Run pip install enum34
+
+
+class State(Enum):
+    unvisited = 1
+    visited = 2
+    visiting = 3
 
 
 class Node:
 
     def __init__(self, id):
         self.id = id
-        self.visited = False
+        self.visit_state = State.unvisited
         self.adjacent = OrderedDict()  # key = node, val = weight
 
     def __str__(self):

graphs_trees/graph/graph_solution.ipynb

@@ -135,13 +135,20 @@
    "source": [
     "%%writefile graph.py\n",
     "from collections import OrderedDict\n",
+    "from enum import Enum  # Python 2 users: Run pip install enum34\n",
+    "\n",
+    "\n",
+    "class State(Enum):\n",
+    "    unvisited = 1\n",
+    "    visited = 2\n",
+    "    visiting = 3\n",
     "\n",
     "\n",
     "class Node:\n",
     "\n",
     "    def __init__(self, id):\n",
     "        self.id = id\n",
-    "        self.visited = False\n",
+    "        self.visit_state = State.unvisited\n",
     "        self.adjacent = OrderedDict()  # key = node, val = weight\n",
     "\n",
     "    def __str__(self):\n",