说明：  设计并实现以下算法：给出用单链表存储多项式的结构，利用后接法生成多项式的单链表结构，实现两个多项式相加的运算，并就地逆置相加后的多项式链式。
(Designed and implemented the following algorithm: given the structure of a singly linked list storage polynomial, use the connection to generate a polynomial single-chain structure, to achieve the operation of two polynomials, and set the sum of in situ reverse polynomial chain.)