as for this description, "However, to get the lexicographically smallest string with K digit C, then the replacement should be performed as follows. Suppose that this step of the algorithm need to change all the numbers that are different from the numbers with modulo I, first time it need replace all digits C + I for digit C from begin to end of string. Second time it need replace all digits C – I for C for end to begin of string, because in need to lexicographically minimum one. ", first, i think it's right,then i think the reason is that: at the first time,the original number is C+I and it will be reduced to C,so we should try to put this smaller one in the first part.Then , at the second time,the original number is C-I,and it will be added to C,so we should put it in the last part.