【leetcode】All Paths From Source to Target

题目如下：

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.

解题思路：题目明确了没有回路，而且nodes的范围是[2,15]，这实在是大大降低了难度，一个深度遍历就能搞定，注意由于结果需要输出path，所以需要记录每次遍历的过程。

代码如下：

class Solution(object):
    def copy(self,src,dest):
        for i in src:
            dest.append(i)
        return dest
    def allPathsSourceTarget(self,graph):
        stack = []
        stack.append([0])
        step = []
        res = []
        while len(stack) > 0:
            path = stack.pop(0)
            if path[-1] == len(graph) - 1:
                res.append(self.copy(path,[]))
            for i in graph[path[-1]]:
                tl = self.copy(path,[])
                tl.append(i)
                stack.insert(0,tl)
        return res