1013_digital_root

代码说明：

  数字根算法，用最简单的代码计算数字根。如果把一个大数的各位数字相加得到一个和，再把这个和的各位数字相加又得一个和，再继续作数字和，直到最后的数字和是个位数为止，这最后的数称为最初那个数的“数字根”。(Digital root algorithm, with the most simple code to calculate the digital root. If you figure in a large numbers is the sum of a, then this and you figure the sum is again a, and then continue for digital and until the final figure and the single digits, the last number called initially that the number of "digital root".)