홀수 짝수 목록 - 순진한 접근 방식

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var oddEvenList = function(head) {
    let odd = [];
    let even = [];
    let current = head;
    let count = 0;
    while (current !== null) {
      if (count % 2 === 0) {
        even.push(current.val);
      } else {
        odd.push(current.val);
      }
      count++;

      current = current.next;
    }
    const newArray = even.concat(odd);

    head = null;

    const insertAtLast = (data) => {
      if (head === null) {
        head = new ListNode(data);
      } else {
        let current = head;
        while (current.next) {
          current = current.next;
        }
        current.next = new ListNode(data);
      }
    };

    for (let i = 0; i < newArray.length; i++) {
      insertAtLast(newArray[i]);
    }

    return head;
};