摘要:
https://www.luogu.org/problemnew/show/P4942 上面为原题地址; 引理: 一个数字除以9的余数等于它的各位数字之和除以9的余数 那么我们将其各个数字加起来%9即可; 当然用等差数列公式更快; 阅读全文
摘要:
Try guessing the statement from this picture: You are given a non-negative integer d . You have to find two non-negative real numbers a and b such tha 阅读全文