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.

无循环图的路径搜索问题。

class Solution {
public:
    void helper(vector<vector<int>>& graph, vector<vector<int>> &res, 
                vector<int> &temp, int &Target) {
        if (temp.back() == Target) {
            res.push_back(temp);
            return;
        }
        vector<int> rt = graph[temp.back()];
        for (int i=0; i<rt.size(); ++i) {
            temp.push_back(rt[i]);
            helper(graph, res, temp, Target);
            temp.pop_back();
        }
        
        
    }
    vector<vector<int>> allPathsSourceTarget(vector<vector<int>>& graph) {
        int Target = graph.size() - 1;
        vector<vector<int>> res;
        vector<int> temp;
        if (Target < 0)
            return res;
        temp.push_back(0);
        helper(graph, res, temp, Target);
        return res;
    }
};