797. All Paths From Source to Target ⭐

Medium

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.

解題

func allPathsSourceTarget(graph [][]int) [][]int {
    // DAG 有相無環，所以可以不用記走過哪些點
    res := make([][]int, 0)

    var helper func(int, []int)
    helper = func(cur int, path []int) {
        path = append(path, cur)
        if cur == len(graph) - 1 {
            temp := make([]int, len(path));
            copy(temp, path) 
            res = append(res, temp)
        } else {
            for _, n := range graph[cur] {
                helper(n, path)
            }
        }
    }

    helper(0, []int{})

    return res
}