[LeetCode]All Paths From Source to Target

题目描述：

LeetCode 797. All Paths From Source to Target

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.

题目大意：

给定有向无环图（DAG），求从0号节点出发到N - 1的所有路径。

解题思路：

DFS（深度优先搜索）

Python代码：

class Solution(object):
    def allPathsSourceTarget(self, graph):
        """
        :type graph: List[List[int]]
        :rtype: List[List[int]]
        """
        ans = []
        def dfs(x, path):
            if x == len(graph) - 1: ans.append(path)
            for z in graph[x]: dfs(z, path + [z])
        dfs(0, [0])
        return ans