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:
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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:
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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
}