Use set or not

#include "Solution.hpp"
class Solution;

class Node {
public:

    Node (int val) {
        this->val = val;
        this->next = NULL;
    }
    int val;
    Node *next;

    friend class Solution;

};


// only for the 1st Node
//void initNode(Node *head,int n){
//    head->val = n;
//    head->next =NULL;
//}


class Solution {
public:
    // add Node
    void initList () {
        head = new Node(0);
    }
    void addNode(int n) {
        Node *newNode = new Node(n);

        Node *cur = head;
        while (cur->next != NULL) {
            cur = cur->next;
        }
        cur->next = newNode;
    }
    void PrintList(){

        if (head->next == NULL) {                      // 如果first node指向NULL, 表示list沒有資料
            cout << "List is empty.\n";
            //cout <<"head "<<head->val<<endl;
            return;
        }

        Node *cur = head;             // 用pointer *current在list中移動
        while (cur != NULL) {                 // Traversal
            cout << cur->val << " ";
            cur = cur->next;
        }
        cout << endl;
    }
    void deleteDuplicate() {
        //Node* dummy = new Node(0);
        //dummy->next = head;
        Node* cur;
        Node* newHead = head;
        while (newHead != NULL && newHead->next != NULL) {
            cur = newHead;
            while (cur->next != NULL) {
                if (cur->next->val == newHead->val) {
                    cur->next = cur->next->next;
                } else {
                    cur = cur->next;
                }
            }
            newHead = newHead->next;
        }
    }
    void deleteDuplicateHash() {
        Node* cur = head;
        unordered_set<int> myset;
        while (cur != NULL && cur->next != NULL) {
            if (myset.find(cur->val) == myset.end()) {
                myset.insert(cur->val);
            }
            while (myset.find(cur->next->val) != myset.end()) {
                cur->next = cur->next->next;

            }

            cur = cur->next;
         }
    }

private:
    Node* head;
};