LeetCode OJ

这道题较简单，这里不多说，下面是AC的代码：

/**
     * 插入排序的算法比较简单，我看wiki上，当要在已排序列表中插入一个元素时，是从后到前遍历，
     * 由于链表只能从前往后遍历，所以我采用从后到前。
     * 要注意的地方就是找到位置时，处理链表的元素插入的具体细节
     * @param head
     * @return
     */
    public ListNode insertionSortList(ListNode head){
        //当链表为空或者只有一个节点的情况
        if(head == null || head.next == null)
            return head;
        
        ListNode newHead = head;//记录新的链表头
        ListNode p1 = head, pp1= null, pointer,pPointer = head, temp = null;
        for( pointer = head.next;pointer!=null;pointer = temp)
        {
            pp1 = null;
            p1 = newHead;
            while(p1!= pointer && p1.val<=pointer.val)
            {
                pp1 = p1;
                p1 = p1.next;
            }
            temp = pointer.next;
            
            if(pp1 == null)
            {
                pointer.next = p1;
                newHead = pointer;
                pPointer.next = temp;
            }else if(p1 != pointer){
                pPointer.next = pointer.next;
                pp1.next = pointer;
                pointer.next = p1;
            }
            else
                pPointer = pPointer.next;
            
        }
        return newHead;
    }