对单链表实现就地逆置,即利用原表的存储空间将线性表（a1,a2,…,an）逆置为（an,an-1,…,a1）。输入数据：文本文件input.txt

文件分2行：

第1行是单链表的数据元素个数n，n<20。如果n<1或n>19则视为输入数据出错。

第2行是单链表的n个数据元素，每个元素都是-999～999之间的十进制整数，元素之间用空格分开。

输出数据：文件output.txt

文件只有1行：

第1行是完成逆置之后的单链表n个元素的十进制整数，每个元素之间用空格分开。

如果输入数据出错，或者运行过程出错、问题无解等，则第1行输出字符串“ERROR”。

-Single linked list implementation situ reverse position, namely the use of the storage space of the original tables linear table (a1, a2, ..., an) inverse set (an, an-1, ..., a1). Input data: text file input.txt file sub 2 lines: Line 1 is the number of a single list of data elements n, n < 20. If n < 1 or n>　19 is considered to input data error. The second line is a single-chain n data elements, and each element is a decimal integer between-999 to 999, separated by a space between the elements. Output data: file output.txt file has only one line: Line 1 is set after the completion of the reverse single linked list of n decimal integer elements, separated by a space between each element. If the input data error, or an error during the operation, the problem has no solution, etc., then the first line of the output string " ERROR" .