3217. 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:

Remove the nodes with values 1, 2, and 3.

Example 2:

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

Output: [2,2,2]

Explanation:

Remove the nodes with value 1.

Example 3:

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

Output: [1,2,3,4]

Explanation:

No node has value 5.

Constraints:

• 1 <= nums.length <= 105
• 1 <= nums[i] <= 105
• All elements in nums are unique.
• The number of nodes in the given list is in the range [1, 105].
• 1 <= Node.val <= 105
• The input is generated such that there is at least one node in the linked list that has a value not present in nums.

Solution:

/**
 * 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) {
        Set<Integer> set = new HashSet<Integer>();

        for (int i = 0; i < nums.length; i++){
            set.add(nums[i]);
        }

        //  -1   4 5
        //  pre->
        //         cur 

        // -1 2 10 9
        // p 
        //      c 
        // 
        // -1 -> 10 -> 9
        //       p   
        // 
        ListNode dummy = new ListNode(-1);
        ListNode prev = dummy;
        ListNode cur = head;
        while(cur != null){
            if (set.contains(cur.val)){
                cur = cur.next;
                prev.next = cur;
            }else{
                prev.next = cur;
                prev = cur;
                cur = cur.next;
            }

        }





        return dummy.next;
    }
}