scientific-programming-exercises/exam/ex01/connectivity.py

from collections import deque

from cfg import config
from db_util import get_page_id

def can_reach(title, connection):
	page = get_page_id(title, connection)
	cursor = connection.cursor()
	cursor.execute("SELECT COUNT(destination) FROM links WHERE destination=%s", (page, ))
	count = cursor.fetchone()[0]
	return count > 0

def shortest_path(center, title, connection):
	if(not can_reach(title, connection)):
		return []

	cursor = connection.cursor()
	current_page = get_page_id(title, connection)
	center_page = get_page_id(center, connection)
	path = deque()
	while(current_page != center_page):
		path.append(current_page)
		cursor.execute('''SELECT links.source 
				FROM links
				LEFT JOIN dijkstra_helper ON links.destination=dijkstra_helper.page
				WHERE links.destination=%s
				ORDER BY dijkstra_helper.value ASC
				LIMIT 1''', (current_page,))
		current_page = cursor.fetchone()[0]
	return list(reversed(path))