https://www.nowcoder.com/practice/d8b6b4358f774294a89de2a6ac4d9337

非递归

之前好像在《算法笔记》上做过，是某种排序算法思想？

  1. public ListNode Merge(ListNode list1, ListNode list2) {
  2.     ListNode head = new ListNode(0);
  3.     ListNode node = head;
  4.     while (list1 != null && list2 != null) {
  5.         if (list1.val <= list2.val) {
  6.             node.next = list1;
  7.             node = list1;
  8.             list1 = list1.next;
  9.         } else {
  10.             node.next = list2;
  11.             node = list2;
  12.             list2 = list2.next;
  14.         }
  15.     }
  17.     while (list2 != null) {
  18.         node.next = list2;
  19.         node = list2;
  20.         list2 = list2.next;
  22.     }
  24.     while (list1 != null) {
  25.         node.next = list1;
  26.         node = list1;
  27.         list1 = list1.next;
  28.     }
  30.     return head.next;
  31. }