稀疏矩阵三元组单链表 使用单链表作为成员变量声明稀疏矩阵三元组单链表类，实现构造、矩阵相加（+=和+）、比较相等、转置等功能-Single linked list sparse matrix triples Use single linked list as a member variable declaration sparse matrix triples singly linked list class that implements the structure, matrix a