摘要：狄利克雷卷积 定义 设f,g为两个数论函数. 定义卷积运算(f×g)(n)=∑d|n[f(d)∗g(n/d)] 运算律 交换律:f×g=g×f 结合律:(f×g)×h=f×(g×h) 存在单位元ι使得f=ι×f 根据定义. (ι×f)(n)=∑d|nι(d)∗f(nd)=f(n) 所以可知. l(n 阅读全文

摘要：There is a legendary tale about Dragon Balls on Planet X: if one collects seven Dragon Balls, the Dragon God will show up and help you fulfill your wi 阅读全文

摘要：D. Minimax Problem time limit per test 5 seconds memory limit per test 512 megabytes input standard input output standard output You are given nn arra 阅读全文