leetcode797. All possible paths (medium)

Ideas ： acyclic -> dfs Find a path , Until arrival n - 1
Be careful ： Memorize dfs（ Save a node to n-1 The path of ） Not optimized , This is because structure ans Complexity and directness dfs The complexity is the same , It doesn't really optimize -> I have tried to write code , It was used Memorization is even slower ...

class Solution {
    
public:

    vector<vector<int>> ans;
    vector<int> path;
    void dfs(vector<vector<int>>& graph, int index) {
    
        int n = graph.size();
        if (index == n - 1) ans.push_back(path); 
        for (auto& a : graph[index]) {
    
            path.push_back(a);
            dfs(graph, a);
            path.pop_back();
        }
    }
    vector<vector<int>> allPathsSourceTarget(vector<vector<int>>& graph) {
    
 
        path.push_back(0);
        dfs(graph, 0);
        return ans;
    }
};