From 8e02504f1528ee3b013f21fbb47c941a637e0829 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Daniel=20Kn=C3=BCttel?= Date: Thu, 21 Feb 2019 17:14:35 +0100 Subject: [PATCH] those files are needed --- exam/ex01/db_util.py | 28 +++++++++++++++++++++++ exam/ex01/graph.py | 54 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 82 insertions(+) create mode 100644 exam/ex01/db_util.py create mode 100644 exam/ex01/graph.py diff --git a/exam/ex01/db_util.py b/exam/ex01/db_util.py new file mode 100644 index 0000000..2884cb1 --- /dev/null +++ b/exam/ex01/db_util.py @@ -0,0 +1,28 @@ +from cfg import config + +def _get_page_id(title, connection): + cursor = connection.cursor() + if(config["use_sqlite"]): + cursor.execute("SELECT rowid FROM pages WHERE title=%s", (title,)) + else: + cursor.execute("SELECT page_id FROM pages WHERE title=%s", (title,)) + return cursor.fetchone() + +def get_page_id(title, connection): + + result = _get_page_id(title, connection) + if(result is not None): + return result[0] + + cursor = connection.cursor() + cursor.execute("INSERT INTO pages(title) VALUES(%s)", (title,)) + return _get_page_id(title, connection)[0] + +def get_page_title(page_id, connection): + cursor = connection.cursor() + if(config["use_sqlite"]): + cursor.execute("SELECT title FROM pages WHERE rowid=%s", (page_id,)) + else: + cursor.execute("SELECT title FROM pages WHERE page_id=%s", (page_id,)) + return cursor.fetchone()[0] + diff --git a/exam/ex01/graph.py b/exam/ex01/graph.py new file mode 100644 index 0000000..6865c94 --- /dev/null +++ b/exam/ex01/graph.py @@ -0,0 +1,54 @@ +from collections import deque, defaultdict +import logging + +from cfg import config + +logger = logging.getLogger(__name__) + + +class DijkstraHelper(object): + def __init__(self, nodes, connections): + self._nodes = {node: float("inf") for node in nodes} + self._connections = connections + self._todo_in_next_step = set() + + @classmethod + def from_db(cls, connection): + cursor = connection.cursor() + cursor.execute("SELECT page_id FROM pages") + nodes = [n[0] for n in cursor.fetchall()] + connections = defaultdict(list) + + cursor.execute("SELECT source, destination FROM links") + for source, destination in cursor: + connections[source].append(destination) + + return cls(nodes, connections) + + def dijkstra(self, root): + self.recursive_dijkstra([root], 0) + + def recursive_dijkstra(self, todos, depth): + if(not todos): + return + logger.info("recursive_dijkstra(<{} nodes>, {})".format(len(todos), depth)) + next_todos = deque() + for todo in todos: + next_todos.extend(self.dijkstra_one(todo, depth)) + + self.recursive_dijkstra(next_todos, depth + 1) + + def dijkstra_one(self, node, depth): + for neighbor in self._connections[node]: + if(self._nodes[neighbor] <= depth): + continue + self._nodes[neighbor] = depth + yield neighbor + + def write_back(self, connection): + cursor = connection.cursor() + cursor.execute("DELETE FROM dijkstra_helper") + cursor.executemany("INSERT INTO dijkstra_helper(page, value) VALUES(%s, %s)", list(self._nodes.items())) + + +