Delete Nodes From Linked List Present in Array

                                            Delete Nodes From Linked List Present in Array 



You are given an array of integers nums and the head of a linked list. Return the head of the modified linked list after removing all nodes from the linked list that have a value that exists in nums.


Example 1:


Input: nums = [1,2,3], head = [1,2,3,4,5]


Output: [4,5]


Explanation:



Example 2:


Input: nums = [1], head = [1,2,1,2,1,2]


Output: [2,2,2]


/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode modifiedList(int[] nums, ListNode head) {
          HashSet<Integer> set = new HashSet<>();
        for (int num : nums) {
            set.add(num);  // Store nums in HashSet for fast lookup
        }

        // Step 1: Handle head removal
        while (head != null && set.contains(head.val)) {
            head = head.next; // Move head to next valid node
        }

        // Step 2: Traverse the linked list and remove unwanted nodes
        ListNode current = head;
        while (current != null && current.next != null) {
            if (set.contains(current.next.val)) {
                current.next = current.next.next; // Skip the node
            } else {
                current = current.next; // Move forward
            }
        }

        return head; // Return modified list
       
    }
}


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