Clone a graph

I was doing this problem clone a graph on leetcode but I’m getting “You must return a copy of all the nodes in the original graph” as the output.

it is said in the problem that the graph will not contain any self loop.

Here’s my code-

set<Node*> s;
Node* head=nullptr;

Node* dfs(Node* root, Node* prev, Node* copyofprevnode){
    Node* newNode = new Node(root->val,{});
    if(head==nullptr) head = newNode; // this line executes only once just to store the 1st node of cloned graph
    if(copyofprevnode!=nullptr) newNode->neighbors.push_back(copyofprevnode);
    for(auto x : root->neighbors){
        if(x!=prev && s.count(x)==0) newNode->neighbors.push_back(dfs(x,root,newNode));
    return newNode;

Node* cloneGraph(Node* node) {
    return head;

Can anybody help?