51.算法->合并两个排序的链表

day4：算法->合并两个排序的链表

思路：同时遍历两个链表，比较当前值大小，剩余的直接往后进行追加

var mergeTwoLists = function (l1, l2) {
//声明一个链表用来存储结果
  let newlist = new ListNode(0);
//定义指针
  let head = newlist;
  while (l1 && l2) {
    if (l1.val < l2.val) {
      head.next = l1;
      l1 = l1.next;
    } else {
      head.next = l2;
      l2 = l2.next;
    }
//移动head
    head = head.next;
  }
//剩余元素追加
  if (l1) {
    head.next = l1;
  }
  if (l2) {
    head.next = l2;
  }
  return newlist.next;
};