Given a directed, acyclic graph of N nodes.  Find all possible paths from node 0 to node N-1, and return them in any order.
The graph is given as follows:  the nodes are 0, 1, ..., graph.length - 1.  graph[i] is a list of all nodes j for which the edge (i, j) exists.
Example:
Input: [[1,2], [3], [3], []] 
Output: [[0,1,3],[0,2,3]] 
Explanation: The graph looks like this:
0--->1
|    |
v    v
2--->3
There are two paths: 0 -> 1 -> 3 and 0 -> 2 -> 3.
Note:
       The number of nodes in the graph will be in the range [2, 15].
       You can print different paths in any order, but you should keep the order of nodes inside one path.
class Solution:
     def numRabbits(self, answers):
         """
         :type answers: List[int]
         :rtype: int
         """
         total = 0
         d = collections.defaultdict(int)
         for ans in answers:
             d[ans] += 1
         for k, v in d.items():
             total += math.ceil(v/(k+1)) * (k+1)
         return total
class Solution:
     def numRabbits(self, answers):
         """
         :type answers: List[int]
         :rtype: int
         """
         total = 0
         d = collections.defaultdict(int)
         for ans in answers:
             d[ans] += 1
         for k, v in d.items():
             total += math.ceil(v/(k+1)) * (k+1)
         return total