# 12. All Paths From Source to Target

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:**

![](https://assets.leetcode.com/uploads/2020/09/28/all_1.jpg)

```
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:**

![](https://assets.leetcode.com/uploads/2020/09/28/all_2.jpg)

```
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]]
```

```
Example 3:
Input: graph = [[1],[]]
Output: [[0,1]]

Example 4:
Input: graph = [[1,2,3],[2],[3],[]]
Output: [[0,1,2,3],[0,2,3],[0,3]]


Example 5:
Input: graph = [[1,3],[2],[3],[]]
Output: [[0,1,2,3],[0,3]]
```

## Solution: (DFS)

```cpp
class Solution
{
public:
    void dfs(vector<vector<int>> graph, int src, int dest, vector<int> v, vector<vector<int>> &res)
    {

        if (src == dest)
        {
            v.push_back(src);
            res.push_back(v);
            return;
        }

        v.push_back(src);
        for (int i = 0; i < graph[src].size(); i++)
        {
            dfs(graph, graph[src][i], dest, v, res);
        }

        return;
    }

    vector<vector<int>> allPathsSourceTarget(vector<vector<int>> &graph)
    {

        vector<int> v;
        vector<vector<int>> res;
        int n = graph.size();
        dfs(graph, 0, n - 1, v, res);
        return res;
    }
};
```

## Optimized some space by reusing the vector:

```cpp
class Solution
{
public:
    void dfs(vector<vector<int>> graph, int src, int dest, vector<int> &v, vector<vector<int>> &res)
    {

        if (src == dest)
        {
            v.push_back(src);
            res.push_back(v);
            v.pop_back();
            return;
        }

        v.push_back(src);
        for (int i = 0; i < graph[src].size(); i++)
        {
            dfs(graph, graph[src][i], dest, v, res);
        }
        v.pop_back();

        return;
    }

    vector<vector<int>> allPathsSourceTarget(vector<vector<int>> &graph)
    {

        vector<int> v;
        vector<vector<int>> res;
        int n = graph.size();
        dfs(graph, 0, n - 1, v, res);
        return res;
    }
};
```

**Time Complexity: O(v^v)**


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