leetcode-328 奇偶链表

/**
 * 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) {
  if (!head) return null;
  let cur = head,
    count = 1;
  let head2 = null,
    cur2 = null,
    prev = null;
  while (cur) {
    // 偶数
    if (count % 2 === 0) {
      if (!head2) {
        head2 = cur;
        cur2 = head2;
        prev.next = cur.next;
        cur = cur.next;
        cur2.next = null;
      } else {
        cur2.next = cur;
        prev.next = cur.next;
        cur = cur.next;
        cur2.next.next = null;
        cur2 = cur2.next;
      }
    } else {
      prev = cur;
      cur = cur.next;
    }
    count++;
  }
  prev.next = head2;
  return head;
};