gistfile1.txt

class Node(object):
	def __init__(self, _children):
		self.memo = None
		self.children = _children

dest = Node([])
source = Node([
	dest,         # source -> dest
	Node([dest]), # source -> intermediate -> dest
	Node([Node([dest])]), # source -> a -> b -> dest
	Node([]) # source -> intermediate -> nothing
	])

def paths_to_dest(node):
	if node == dest:
		return 1
	else:
		if node.memo is None:
			node.memo = sum([paths_to_dest(child) for child in node.children])
		return node.memo

print paths_to_dest(source)