GitHub/interactive-coding-challenges
1
0
Fork 0
mirror of https://github.com/donnemartin/interactive-coding-challenges synced 2026-01-06 17:38:02 +00:00
Code Issues Packages Projects Releases Wiki Activity

Rework graph challenge and solution (#90)

Browse Source
This commit is contained in:
Donne Martin
2016-07-04 07:16:15 -04:00
committed by GitHub
parent 618eeedfe3
commit cb660acd13
4 changed files with 254 additions and 118 deletions
Download Patch File Download Diff File Expand all files Collapse all files

163
graphs_trees/graph/graph_solution.ipynb
View File

@@ -37,7 +37,11 @@
" * Implement both\n",
"* Do the edges have weights?\n",
" * Yes\n",
"* Can we assume the inputs are valid?\n",
"* If we try to add a node that already exists, do we just do nothing?\n",
" * Yes\n",
"* If we try to delete a node that doesn't exist, do we just do nothing?\n",
" * Yes\n",
"* Can we assume this fits memory?\n",
" * Yes"
]
},
@@ -80,13 +84,24 @@
"Node will keep track of its:\n",
"* id\n",
"* visit state\n",
"* adjacent\n",
" * key: node\n",
" * value: weight\n",
"* incoming edge count (useful for algorithms such as topological sort)\n",
"* adjacent nodes and edge weights\n",
"\n",
"#### add_neighhbor\n",
"\n",
"* Add the neighbor as a key and the weight as the value to `adjacent`\n",
"* If the neighbor doesn't already exist as an adjacent node\n",
" * Update the adjancet nodes and edge weights\n",
" * Increment the neighbor's incoming edge count\n",
"\n",
"Complexity:\n",
"* Time: O(1)\n",
"* Space: O(1)\n",
"\n",
"#### remove_neighhbor\n",
"\n",
"* If the neighbor exists as an adjacent node\n",
" * Decrement the neighbor's incoming edge count\n",
" * Remove the neighbor as an adjacent node\n",
"\n",
"Complexity:\n",
"* Time: O(1)\n",
@@ -96,13 +111,12 @@
"\n",
"Graph will keep track of its:\n",
"* nodes\n",
" * key: node id\n",
" * value: node\n",
"\n",
"#### add_node\n",
"\n",
"* Create a node with the input id\n",
"* Add the newly created node to the list of nodes\n",
"* If node already exists, return it\n",
"* Create a node with the given id\n",
"* Add the newly created node to the collection of nodes\n",
"\n",
"Complexity:\n",
"* Time: O(1)\n",
@@ -110,10 +124,15 @@
"\n",
"#### add_edge\n",
"\n",
"* If the source node is not in the list of nodes, add it\n",
"* If the dest node is not in the list of nodes, add it\n",
"* If the source node is not in the collection of nodes, add it\n",
"* If the dest node is not in the collection of nodes, add it\n",
"* Add a connection from the source node to the dest node with the given edge weight\n",
"\n",
"#### add_undirected_edge\n",
"\n",
"* Call add_edge\n",
"* Also add a connection from the dest node to the source node with the given edge weight\n",
"\n",
"Complexity:\n",
"* Time: O(1)\n",
"* Space: O(1)"
@@ -154,38 +173,66 @@
"\n",
"class Node:\n",
"\n",
" def __init__(self, id):\n",
" self.id = id\n",
" def __init__(self, key):\n",
" self.key = key\n",
" self.visit_state = State.unvisited\n",
" self.adjacent = {} # key = node, val = weight\n",
" self.incoming_edges = 0\n",
" self.adj_nodes = {} # Key = key, val = Node\n",
" self.adj_weights = {} # Key = key, val = weight\n",
"\n",
" def __str__(self):\n",
" return str(self.id)\n",
" def __repr__(self):\n",
" return str(self.key)\n",
"\n",
" def __lt__(self, other):\n",
" return self.key < other.key\n",
"\n",
" def add_neighbor(self, neighbor, weight=0):\n",
" self.adjacent[neighbor] = weight\n",
" if neighbor is None:\n",
" raise Exception('Invalid neighbor')\n",
" neighbor.incoming_edges += 1\n",
" self.adj_weights[neighbor.key] = weight\n",
" self.adj_nodes[neighbor.key] = neighbor\n",
"\n",
" def remove_neighbor(self, neighbor):\n",
" if neighbor is None:\n",
" raise Exception('Invalid neighbor')\n",
" if neighbor.key in self.adj_nodes:\n",
" neighbor.incoming_edges -= 1\n",
" del self.adj_weights[neighbor.key]\n",
" del self.adj_nodes[neighbor.key]\n",
" else:\n",
" raise Exception('Invalid neighbor')\n",
"\n",
"\n",
"class Graph:\n",
"\n",
" def __init__(self):\n",
" self.nodes = {} # key = node id, val = node\n",
" self.nodes = {} # Key = key, val = Node\n",
"\n",
" def add_node(self, id):\n",
" node = Node(id)\n",
" self.nodes[id] = node\n",
" return node\n",
" def add_node(self, key):\n",
" if key is None:\n",
" raise Exception('Invalid key')\n",
" if key in self.nodes:\n",
" return self.nodes[key]\n",
" self.nodes[key] = Node(key)\n",
" return self.nodes[key]\n",
"\n",
" def add_edge(self, id_source, id_dest, weight=0):\n",
" if id_source not in self.nodes:\n",
" self.add_node(id_source)\n",
" if id_dest not in self.nodes:\n",
" self.add_node(id_dest)\n",
" self.nodes[id_source].add_neighbor(self.nodes[id_dest], weight)\n",
" def add_edge(self, source_key, dest_key, weight=0):\n",
" if source_key is None or dest_key is None:\n",
" raise Exception('Invalid key')\n",
" if source_key not in self.nodes:\n",
" self.add_node(source_key)\n",
" if dest_key not in self.nodes:\n",
" self.add_node(dest_key)\n",
" self.nodes[source_key].add_neighbor(self.nodes[dest_key],\n",
" weight)\n",
"\n",
" def add_undirected_edge(self, source, dest, weight=0):\n",
" self.add_edge(source, dest, weight)\n",
" self.nodes[dest].add_neighbor(self.nodes[source], weight)"
" def add_undirected_edge(self, source_key, dest_key, weight=0):\n",
" if source_key is None or dest_key is None:\n",
" raise Exception('Invalid key')\n",
" self.add_edge(source_key, dest_key, weight)\n",
" self.nodes[dest_key].add_neighbor(self.nodes[source_key],\n",
" weight)"
]
},
{
@@ -230,13 +277,12 @@
"\n",
" def create_graph(self):\n",
" graph = Graph()\n",
" for id in range(0, 6):\n",
" graph.add_node(id)\n",
" for key in range(0, 6):\n",
" graph.add_node(key)\n",
" return graph\n",
"\n",
" def test_graph(self):\n",
" graph = self.create_graph()\n",
"\n",
" graph.add_edge(0, 1, weight=5)\n",
" graph.add_edge(0, 5, weight=2)\n",
" graph.add_edge(1, 2, weight=3)\n",
@@ -247,33 +293,46 @@
" graph.add_edge(5, 4, weight=8)\n",
" graph.add_edge(5, 2, weight=9)\n",
"\n",
" assert_equal(graph.nodes[0].adjacent[graph.nodes[1]], 5)\n",
" assert_equal(graph.nodes[0].adjacent[graph.nodes[5]], 2)\n",
" assert_equal(graph.nodes[1].adjacent[graph.nodes[2]], 3)\n",
" assert_equal(graph.nodes[2].adjacent[graph.nodes[3]], 4)\n",
" assert_equal(graph.nodes[3].adjacent[graph.nodes[4]], 5)\n",
" assert_equal(graph.nodes[3].adjacent[graph.nodes[5]], 6)\n",
" assert_equal(graph.nodes[4].adjacent[graph.nodes[0]], 7)\n",
" assert_equal(graph.nodes[5].adjacent[graph.nodes[4]], 8)\n",
" assert_equal(graph.nodes[5].adjacent[graph.nodes[2]], 9)\n",
" assert_equal(graph.nodes[0].adj_weights[graph.nodes[1].key], 5)\n",
" assert_equal(graph.nodes[0].adj_weights[graph.nodes[5].key], 2)\n",
" assert_equal(graph.nodes[1].adj_weights[graph.nodes[2].key], 3)\n",
" assert_equal(graph.nodes[2].adj_weights[graph.nodes[3].key], 4)\n",
" assert_equal(graph.nodes[3].adj_weights[graph.nodes[4].key], 5)\n",
" assert_equal(graph.nodes[3].adj_weights[graph.nodes[5].key], 6)\n",
" assert_equal(graph.nodes[4].adj_weights[graph.nodes[0].key], 7)\n",
" assert_equal(graph.nodes[5].adj_weights[graph.nodes[4].key], 8)\n",
" assert_equal(graph.nodes[5].adj_weights[graph.nodes[2].key], 9)\n",
"\n",
" assert_equal(graph.nodes[0].incoming_edges, 1)\n",
" assert_equal(graph.nodes[1].incoming_edges, 1)\n",
" assert_equal(graph.nodes[2].incoming_edges, 2)\n",
" assert_equal(graph.nodes[3].incoming_edges, 1)\n",
" assert_equal(graph.nodes[4].incoming_edges, 2)\n",
" assert_equal(graph.nodes[5].incoming_edges, 2)\n",
"\n",
" graph.nodes[0].remove_neighbor(graph.nodes[1])\n",
" assert_equal(graph.nodes[1].incoming_edges, 0)\n",
" graph.nodes[3].remove_neighbor(graph.nodes[4])\n",
" assert_equal(graph.nodes[4].incoming_edges, 1)\n",
"\n",
" assert_equal(graph.nodes[0] < graph.nodes[1], True)\n",
"\n",
" print('Success: test_graph')\n",
"\n",
" def test_graph_undirected(self):\n",
" graph = self.create_graph()\n",
"\n",
" graph.add_undirected_edge(0, 1, weight=5)\n",
" graph.add_undirected_edge(0, 5, weight=2)\n",
" graph.add_undirected_edge(1, 2, weight=3)\n",
"\n",
" assert_equal(graph.nodes[0].adjacent[graph.nodes[1]], 5)\n",
" assert_equal(graph.nodes[1].adjacent[graph.nodes[0]], 5)\n",
" assert_equal(graph.nodes[0].adjacent[graph.nodes[5]], 2)\n",
" assert_equal(graph.nodes[5].adjacent[graph.nodes[0]], 2)\n",
" assert_equal(graph.nodes[1].adjacent[graph.nodes[2]], 3)\n",
" assert_equal(graph.nodes[2].adjacent[graph.nodes[1]], 3)\n",
" assert_equal(graph.nodes[0].adj_weights[graph.nodes[1].key], 5)\n",
" assert_equal(graph.nodes[1].adj_weights[graph.nodes[0].key], 5)\n",
" assert_equal(graph.nodes[0].adj_weights[graph.nodes[5].key], 2)\n",
" assert_equal(graph.nodes[5].adj_weights[graph.nodes[0].key], 2)\n",
" assert_equal(graph.nodes[1].adj_weights[graph.nodes[2].key], 3)\n",
" assert_equal(graph.nodes[2].adj_weights[graph.nodes[1].key], 3)\n",
"\n",
" print('Success: test_graph')\n",
" print('Success: test_graph_undirected')\n",
"\n",
"\n",
"def main():\n",
@@ -298,7 +357,7 @@
"output_type": "stream",
"text": [
"Success: test_graph\n",
"Success: test_graph\n"
"Success: test_graph_undirected\n"
]
}
],