147. Insertion Sort List

Sort a linked list using insertion sort.

代码如下：

 /**
  * Definition for singly-linked list.
  * public class ListNode {
  *     int val;
  *     ListNode next;
  *     ListNode(int x) { val = x; }
  * }
  */
 public class Solution {
     public ListNode insertionSortList(ListNode head) {
         if(head==null||head.next==null)
         return head;

         ListNode pre=head;
         ListNode q=head.next;
         ListNode p=head;
         while(q!=null)
         {

             if(q.val<=head.val)
             {
                 pre.next=q.next;
                 q.next=head;
                 head=q;
                 if(pre.next==null)
                 break;
                 else q=pre.next;
                 p=head;
             }
             else
             if(q.val>=p.val&&q.val<p.next.val)
             {
                 pre.next=q.next;
                 q.next=p.next;
                 p.next=q;
                 if(pre.next==null)
                 break;
                 else q=pre.next;
                 p=head;
             }
             else if(q.val>=p.val&&q.val>p.next.val)
             { p=p.next;
             }
             else if(q.val==p.next.val&&p.next!=q)//用于有重复元素时的排序
             {p=p.next;}
             else {
                 p=head;
                 pre=pre.next;
                 q=pre.next;
             }
             ListNode c=head;

         }

         return head;
     }

 }