147. Insertion Sort List

    /*
     * 147. Insertion Sort List 
     * 2016-6-1 by Mingyang 
     * insertion sort的基本思路要有，两个while循环，一次过，对于每一个值与pree开始的
     * list的节点依次比较，然后分别进行插入操作
     */

  public ListNode insertionSortList(ListNode head) {
        if(head==null||head.next==null)
          return head;
         ListNode pre=new ListNode(-1);
         while(head!=null){
             if(pre.next==null){
                pre.next=new ListNode(head.val);
             }else{
                ListNode pree=pre;
                while(pree.next!=null&&pree.next.val<head.val){
                    pree=pree.next;
                }
                ListNode temp=pree.next;
                pree.next=new ListNode(head.val);
                pree.next.next=temp;
             }
             head=head.next;
         }
         return pre.next;
    }