The function takes the argument of the current node index, adjacency list (stored in vector of vectors in this example), and vector of boolean to keep track of which node has been visited.

```
void dfs(int node, vector<vector<int>>* graph, vector<bool>* visited) {
// check whether node has been visited before
if((*visited)[node])
return;
// set as visited to avoid visiting the same node twice
(*visited)[node] = true;
// perform some action here
cout << node;
// traverse to the adjacent nodes in depth-first manner
for(int i = 0; i < (*graph)[node].size(); ++i)
dfs((*graph)[node][i], graph, visited);
}
```