"""
 day12.py

 advent of code, day 12

 We're working on a toy graph first,

      5
      |
   0--1--3    6--7
   |             |
   2--4          8

"""

graph = { 0 : [1, 2],
          1 : [0, 3, 5],
          2 : [0, 4],
          3 : [1],
          4 : [2],
          5 : [1],
          6 : [7],
          7 : [6, 8],
          8 : [7]
        }

def count_connected(id, seen):
    """ Return number of connected nodes.
        >>> len(count_connected(0, set()))
        6
        >>> len(count_connected(7, set()))
        3
    """
    seen.add(id)
    for node in graph[id]:
        if node not in seen:
            seen = count_connected(node, seen)
    return seen

def main():
    answer_seen = count_connected(0, set())
    print "answer is ", len(answer_seen)

if __name__ == "__main__":
    import doctest
    doctest.testmod()
    main()