编程实现合并两个有序(假定为降序)单链表的函数，输入为两个有序链表的头结点，函数返回合并后新的链表的头节点，

要求：不能另外开辟新的内存存放合并的链表。

递归方式：

        /*
      * 递归方式
     */
    public LinkNode MergeLinkList(LinkNode head1,LinkNode head2){
        if(head1 == null)
            return head2;
        if (head2 == null)
            return head1;
        LinkNode mergeHead = null;
        if(head1.value < head2.value){
            mergeHead = head1;
            mergeHead.next = MergeLinkList(head1.next,head2);
        }
        else
        {
            mergeHead = head2;
            mergeHead.next = MergeLinkList(head1,head2.next);
        }
        return mergeHead;
    }    

非递归方式：

        /*
     * 非递归方式
     */
    public LinkNode MergeLinkList_1(LinkNode head1,LinkNode head2){
        if(head1 == null)
            return head2;
        if (head2 == null)
            return head1;
        LinkNode mergeHead;
        LinkNode temp1 = null;
        LinkNode temp2 = null;
        if(head1.value < head2.value){
            mergeHead = head1;
            temp1 = head1.next;
            temp2 = head2;
        }else{
            mergeHead = head2;
            temp1 = head1;
            temp2 = head2.next;
        }
        LinkNode temp = mergeHead;
        while(temp1!=null || temp2 !=null){
            if(temp1.value < temp2.value){
                temp.next = temp1;
                temp = temp1;
                temp1 = temp1.next;
            }else{
                temp.next = temp1;
                temp = temp2;
                temp2 = temp2.next;
            }
        }
        temp.next = temp1==null ? temp2:temp1;
        return mergeHead;
    }