#### Approach #1: Grouping [Accepted]

Intuition

Instead of thinking about connected components in G, think about them in the linked list. Connected components in G must occur consecutively in the linked list.

Algorithm

Scanning through the list, if node.val is in G and node.next.val isn't (including if node.next is null), then this must be the end of a connected component.

For example, if the list is 0 -> 1 -> 2 -> 3 -> 4 -> 5 -> 6 -> 7, and G = [0, 2, 3, 5, 7], then when scanning through the list, we fulfill the above condition at 0, 3, 5, 7, for a total answer of 4.

Complexity Analysis

• Time Complexity: , where is the length of the linked list with root node head.

• Space Complexity: , to store Gset.