797. All Paths From Source to Target

public List<List<Integer>> allPathsSourceTarget(int[][] graph) {
    List<List<Integer>> res = new ArrayList<>();
    List<Integer> tmp = new ArrayList<>();
    tmp.add(0);
    helper(res, graph, 0, tmp);
    return res;
}

private void helper(List<List<Integer>> res, int[][] graph, int cur, List<Integer> tmp) {
    if (cur == graph.length - 1) {
        res.add(new ArrayList(tmp));
        return;
    }

    for (int i : graph[cur]) {
        tmp.add(i);
        helper(res, graph, i, tmp);
        tmp.remove(tmp.size() - 1);
    }
}