We are given head, the head node of a linked list containing unique integer values.

We are also given the list G, a subset of the values in the linked list.

Return the number of connected components inG, where two values are connected if they appear consecutively in the linked list.

Example 1:

Input:

head: 0-
>
1-
>
2-
>
3
G = [0, 1, 3]817. Linked List Components

Output:
 2

Explanation:

0 and 1 are connected, so [0, 1] and [3] are the two connected components.

Example 2:

Input:

head: 0-
>
1-
>
2-
>
3-
>
4
G = [0, 3, 1, 4]

Output:
 2

Explanation:

0 and 1 are connected, 3 and 4 are connected, so [0, 1] and [3, 4] are the two connected components.

Note:

• If N is the length of the linked list given by head , 1 < = N < = 10000 .
• The value of each node in the linked list will be in the range [0, N - 1] .
• 1 < = G.length < = 10000 .
• G is a subset of all values in the linked list.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public int numComponents(ListNode head, int[] G) {
        if (G == null || G.length == 0) return 0;

        Set<Integer> set = new HashSet<>();
        for (int g : G){
            set.add(g);
        }

        int tail = Integer.MIN_VALUE;
        int count = 0;
        while (head != null){
            if (tail == Integer.MIN_VALUE){
                if (set.contains(head.val)){
                    tail = head.val;
                    count++;    
                    set.remove(head.val);
                }
            }
            else if (set.contains(head.val)){
                tail = head.val;
                set.remove(head.val);
            }
            else{
                tail = Integer.MIN_VALUE;
            }

            head = head.next;
        }

        return count;
    }
}

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public int numComponents(ListNode head, int[] G) {
        Set<Integer> set = new HashSet<>();
        for (int num : G){
            set.add(num);
        }

        int count = 0;
        while (head != null){
            if (set.contains(head.val) && (head.next == null || !set.contains(head.next.val)) ) count++;
            head = head.next;
        }

        return count;
    }
}