1、设单链表中存放着n个字符，设计算法，判断该字符串中是否有中心对称关系。例如：xyzzyx、xyzyx都算是中心对称的字符串。

2、设计算法判断一个算术表达式的圆括号是否配对。（提示：对表达式进行扫描，遇‘(’进栈，遇‘)’退掉栈顶的‘(’，表达式被扫描完毕，栈为空)

3、假设以带头结点的循环链表表示队列，并只设一个指针指向队尾，编写相应的置队空、入队和出队算法。

-Set single linked list storage n characters, design algorithm determines whether the string centrosymmetric relationship. In example: xyzzyx, xyzyx be considered the centrosymmetric string. 2, the design algorithm to determine an arithmetic expression in parentheses is paired. (Hint: scan the expression, in case ' ('　into the stack, in case ' )'　drained away the top of the stack ' ('　expression is scanning is completed, the stack is empty), assumed to take the lead in the circular linked list nodes queue, and allowed only a pointer to the tail, the preparation of the home team empty, enqueue and dequeue algorithm.