Linked List Components
<p>You are given the <code>head</code> of a linked list containing unique integer values and an integer array <code>nums</code> that is a subset of the linked list values.</p>

<p>Return <em>the number of connected components in </em><code>nums</code><em> where two values are connected if they appear <strong>consecutively</strong> in the linked list</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0800-0899/0817.Linked%20List%20Components/images/lc-linkedlistcom1.jpg" style="width: 424px; height: 65px;" />
<pre>
<strong>Input:</strong> head = [0,1,2,3], nums = [0,1,3]
<strong>Output:</strong> 2
<strong>Explanation:</strong> 0 and 1 are connected, so [0, 1] and [3] are the two connected components.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0800-0899/0817.Linked%20List%20Components/images/lc-linkedlistcom2.jpg" style="width: 544px; height: 65px;" />
<pre>
<strong>Input:</strong> head = [0,1,2,3,4], nums = [0,3,1,4]
<strong>Output:</strong> 2
<strong>Explanation:</strong> 0 and 1 are connected, 3 and 4 are connected, so [0, 1] and [3, 4] are the two connected components.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the linked list is <code>n</code>.</li>
	<li><code>1 &lt;= n &lt;= 10<sup>4</sup></code></li>
	<li><code>0 &lt;= Node.val &lt; n</code></li>
	<li>All the values <code>Node.val</code> are <strong>unique</strong>.</li>
	<li><code>1 &lt;= nums.length &lt;= n</code></li>
	<li><code>0 &lt;= nums[i] &lt; n</code></li>
	<li>All the values of <code>nums</code> are <strong>unique</strong>.</li>
</ul>
Array; Hash Table; Linked List
/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    int numComponents(ListNode* head, vector<int>& nums) {
        unordered_set<int> s(nums.begin(), nums.end());
        int ans = 0;
        while (head) {
            while (head && !s.count(head->val)) head = head->next;
            ans += head != nullptr;
            while (head && s.count(head->val)) head = head->next;
        }
        return ans;
    }
};