Added Depth Limited Search in search.ipynb (aimacode#876)

* Added Depth Limited Search in search.ipynb

* Made changes in depth limited search

search.ipynb

@@ -1542,6 +1542,103 @@
     "               problem=romania_problem)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## 7. Depth Limited Search\n",
+    "\n",
+    "Let's change all the 'node_colors' to starting position and define a different problem statement.  \n",
+    "Although we have a working implementation, but we need to make changes."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 17,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def depth_limited_search(problem, frontier, limit = -1):\n",
+    "    '''\n",
+    "    Perform depth first search of graph g.\n",
+    "    if limit >= 0, that is the maximum depth of the search.\n",
+    "    '''\n",
+    "    # we use these two variables at the time of visualisations\n",
+    "    iterations = 0\n",
+    "    all_node_colors = []\n",
+    "    node_colors = {k : 'white' for k in problem.graph.nodes()}\n",
+    "    \n",
+    "    frontier.append(Node(problem.initial))\n",
+    "    explored = set()\n",
+    "    \n",
+    "    cutoff_occurred = False\n",
+    "    node_colors[Node(problem.initial).state] = \"orange\"\n",
+    "    iterations += 1\n",
+    "    all_node_colors.append(dict(node_colors))\n",
+    "      \n",
+    "    while frontier:\n",
+    "        # Popping first node of queue\n",
+    "        node = frontier.pop()\n",
+    "        \n",
+    "        # modify the currently searching node to red\n",
+    "        node_colors[node.state] = \"red\"\n",
+    "        iterations += 1\n",
+    "        all_node_colors.append(dict(node_colors))\n",
+    "        \n",
+    "        if problem.goal_test(node.state):\n",
+    "            # modify goal node to green after reaching the goal\n",
+    "            node_colors[node.state] = \"green\"\n",
+    "            iterations += 1\n",
+    "            all_node_colors.append(dict(node_colors))\n",
+    "            return(iterations, all_node_colors, node)\n",
+    "\n",
+    "        elif limit >= 0:\n",
+    "            cutoff_occurred = True\n",
+    "            limit += 1\n",
+    "            all_node_color.pop()\n",
+    "            iterations -= 1\n",
+    "            node_colors[node.state] = \"gray\"\n",
+    "\n",
+    "        \n",
+    "        explored.add(node.state)\n",
+    "        frontier.extend(child for child in node.expand(problem)\n",
+    "                        if child.state not in explored and\n",
+    "                        child not in frontier)\n",
+    "        \n",
+    "        for n in frontier:\n",
+    "            limit -= 1\n",
+    "            # modify the color of frontier nodes to orange\n",
+    "            node_colors[n.state] = \"orange\"\n",
+    "            iterations += 1\n",
+    "            all_node_colors.append(dict(node_colors))\n",
+    "\n",
+    "        # modify the color of explored nodes to gray\n",
+    "        node_colors[node.state] = \"gray\"\n",
+    "        iterations += 1\n",
+    "        all_node_colors.append(dict(node_colors))\n",
+    "        \n",
+    "    return 'cutoff' if cutoff_occurred else None\n",
+    "\n",
+    "\n",
+    "def depth_limited_search_for_vis(problem):\n",
+    "    \"\"\"Search the deepest nodes in the search tree first.\"\"\"\n",
+    "    iterations, all_node_colors, node = depth_limited_search(problem, Stack())\n",
+    "    return(iterations, all_node_colors, node)     "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "all_node_colors = []\n",
+    "romania_problem = GraphProblem('Arad', 'Bucharest', romania_map)\n",
+    "display_visual(romania_graph_data, user_input=False, \n",
+    "               algorithm=depth_limited_search_for_vis, \n",
+    "               problem=romania_problem)"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},