leetcode-21 合并两个有序链表

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} list1
 * @param {ListNode} list2
 * @return {ListNode}
 */
var mergeTwoLists = function (list1, list2) {
  let cur1 = list1;
  let cur2 = list2;
  const newHead = new ListNode();
  let cur = newHead;
  while (cur1 && cur2) {
    if (cur1.val <= cur2.val) {
      // 摘取cur1节点
      const next = cur1.next;
      cur1.next = null;
      cur.next = cur1;
      cur1 = next;
    } else {
      // 摘取cur2节点
      const next = cur2.next;
      cur2.next = null;
      cur.next = cur2;
      cur2 = next;
    }
    cur = cur.next;
  }
  if (cur1) {
    cur.next = cur1;
  } else if (cur2) {
    cur.next = cur2;
  }
  return newHead.next;
};