摘要：题目 给出n个数qi，给出Fj的定义如下： 令Ei=Fi/qi，求Ei. 思路 年轻人的第一道FFT。 $$ E_j=\sum_{ij}\frac{q_i}{(i j)^2} $$ 设： $$ f[i]=q_i\\ g[i]=\frac{1}{i^2} $$ 那么原式可以化为： $$ E_j=\su 阅读全文

摘要：题目 Bob has a dictionary with N words in it. Now there is a list of words in which the middle part of the word has continuous letters disappeared. The 阅读全文

摘要：题目 As we all know, Harry Porter learns magic at Hogwarts School. However, learning magical knowledge alone is insufficient to become a great magician. 阅读全文