797. All Paths From Source to Target

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[797. All Paths From Source to Target

](https://leetcode.com/problems/all-paths-from-source-to-target/description/)

题目描述

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.

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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，求顶点 0 到 N - 1 的所有路径

解题思路

DFS

代码

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class Solution {
    func allPathsSourceTarget(_ graph: [[Int]]) -> [[Int]] {
        var ans = [[Int]]()
        
        func dfs(list: [Int], path: [Int]) {
            for p in list {
                var new = path
                new.append(p)
                if p == graph.count - 1 {
                    ans.append(new)
                }else {
                    dfs(list: graph[p], path: new)
                }
            }
        }
        dfs(list: graph[0], path: [0])
        return ans
    }
}
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