linked-list-components.js

/**
 * Linked List Components
 *
 * 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 in G, 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]
 * 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.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */

/**
 * @param {ListNode} head
 * @param {number[]} G
 * @return {number}
 */
const numComponents = (head, G) => {
  const set = new Set(G);

  let count = 0;
  let node = head;

  while (node) {
    if (set.has(node.val)) {
      count++;

      while (node && set.has(node.val)) {
        node = node.next;
      }
    } else {
      node = node.next;
    }
  }

  return count;
};

export { numComponents };