3217 - Delete Nodes From Linked List Present in Array

C++

class Solution {
public:
    ListNode* modifiedList(vector<int>& nums, ListNode* head) {
        unordered_set<int> s(nums.begin(), nums.end());
        ListNode* dummy = new ListNode(0, head);
        for (ListNode* pre = dummy; pre->next;) {
            if (s.count(pre->next->val)) {
                pre->next = pre->next->next;
            } else {
                pre = pre->next;
            }
        }
        return dummy->next;
    }
};

JAVA

class Solution {
    public ListNode modifiedList(int[] nums, ListNode head) {
        Set<Integer> s = new HashSet<>();
        for (int x : nums) {
            s.add(x);
        }
        ListNode dummy = new ListNode(0, head);
        for (ListNode pre = dummy; pre.next != null;) {
            if (s.contains(pre.next.val)) {
                pre.next = pre.next.next;
            } else {
                pre = pre.next;
            }
        }
        return dummy.next;
    }
}