Leetcode147. 对链表进行插入排序

题目传送： ​​https://leetcode.cn/problems/insertion-sort-list/​​

运行效率：

代码如下：

class Solution {
   public ListNode insertionSortList(ListNode head) {
    // 处理边界情况
    if (head == null || head.next == null) {
      return head;
    }
    ListNode newHead = new ListNode(head.val);
    head= head.next;
    while (head != null) {
      ListNode listNode = new ListNode(head.val);
      newHead = change(newHead, listNode);
      head = head.next;
    }
    return newHead;
  }
  
//插入排序，把node插入到新链表的适当的位置
  public ListNode change(ListNode head, ListNode node) {
    // 处理边界情况
    if (head.val >= node.val) {
      node.next = head;
      return node;
    }

    ListNode cur = head;
    ListNode prev = head;
    // 先找到node应该插入的位置
    while (cur != null) {
      if (cur.val < node.val) {
        prev = cur;
        cur = cur.next;
      } else {
        break;
      }
    }
    prev.next = node;
    node.next = cur;
    return head;
  }
}