假设稀疏矩阵A和B均以三元组表作为存储结构，试写出矩阵相加和相乘的算法，另设三元组表C存放结果矩阵。(Suppose that the sparse matrix A and B are all three tables as the storage structure, try to write the matrix addition and multiplication algorithm, and set up the three tuple table C to store the result matrix.)