[leetcode] 797. All Paths From Source to Target
阿新 • • 發佈:2022-03-28
題目
Given a directed acyclic graph (DAG) of n
nodes labeled from 0
to n - 1
, find all possible paths from node 0
to node n - 1
and return them in any order.
The graph is given as follows: graph[i]
is a list of all nodes you can visit from node i
(i.e., there is a directed edge from node i
to node graph[i][j]
Example 1:
Input: graph = [[1,2],[3],[3],[]]
Output: [[0,1,3],[0,2,3]]
Explanation: There are two paths: 0 -> 1 -> 3 and 0 -> 2 -> 3.
Example 2:
Input: graph = [[4,3,1],[3,2,4],[3],[4],[]]
Output: [[0,4],[0,3,4],[0,1,3,4],[0,1,2,3,4],[0,1,4]]
Constraints:
n == graph.length
2 <= n <= 15
0 <= graph[i][j] < n
-
graph[i][j] != i
(i.e., there will be no self-loops). - All the elements of
graph[i]
are unique. - The input graph is guaranteed to be a DAG.
思路
回溯,列舉所有可能出現的路徑, 當到達頂點n時返回結果。
程式碼
python版本:
class Solution: def allPathsSourceTarget(self, graph: List[List[int]]) -> List[List[int]]: res = [] def dfs(node, path): if node == len(graph)-1: res.append(path) return [dfs(new_node, path+[new_node]) for new_node in graph[node]] dfs(0, [0]) return res