通过双重循环来控制输出，外层循环控制行数，内层循环控制列。还有个地方需要注意的是，内层和外层之间的联系，内层列的个数是根据外层的行数来控制的。-By double loop to control the output, the outer loop control the number of rows, the inner loop control columns. There is a place to note that the link between the inner and outer layers, the number of the inner layer of the column is the number of rows to the outer layer of control.