用数组来模拟两个大数的乘法操作，避免了溢出的情况。-Array to simulate the operation of multiplication of two large numbers, to avoid overflow.

大数乘法加法，把数字转换成字符串，不论多大都可以运算啦-Large numbers multiplication, addition, converting numbers into strings, regardless of how much can be op!

大数的乘法，结构简单程序思路清晰，易于学习改进，对于初学者来说是个很好的选择-Large numbers of subtraction, while with negative addition. The code is shorter, clearer structure, suitable for beginners who use algorithms