{

"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)"

]

},