显然当且仅当$\gcd(i,j)=1$时才对答案有贡献，化简得\[\begin{eqnarray*}ans&=&\sum_{i=1}^n\sum_{j=1}^i\mu(ij)[\gcd(i,j)=1]\\ &=&\sum_{i=1}^n\sum_{j=1}^i\mu(ij)\sum_{d|i,d.....
分类：
其他好文 时间：
2015-12-21 18:29:12
阅读次数：
142
B. The Best Gift Emily's birthday is next week and Jack has decided to buy a present for her. He knows she loves books so he goes to the local booksh....
分类：
其他好文 时间：
2015-12-20 01:51:17
阅读次数：
192
对于这题本人刚开始的时候觉得应该用DFS来解决实现这个问题，但由于本人对于DFS并不是太熟，所以就放弃了这个想法；但又想了想要按照这个要求实现问题则必须是黑白相间，然后把是字符是'B'或'W'改为'-',即可；下面贴一下我的代码吧 1 #include 2 #include 3 #include 4...
分类：
其他好文 时间：
2015-12-19 00:03:21
阅读次数：
254
#include#define REP(i,a,b) for(int i=a;i pos;bool judge(int l,int r){ if(l>=r) return 1; //coutr){ nex=li;break; } ...
分类：
其他好文 时间：
2015-12-13 17:08:22
阅读次数：
179
Eva loves to collect coins from all over the universe, including some other planets like Mars. One day she visited a universal shopping mall which cou...
分类：
其他好文 时间：
2015-12-06 11:28:02
阅读次数：
156
ArrayTime Limit: 20 SecMemory Limit: 256 MB题目连接http://acm.hdu.edu.cn/showproblem.php?pid=5587DescriptionVicky is a magician who loves math. She has gr...
分类：
其他好文 时间：
2015-11-29 21:20:44
阅读次数：
368
（这篇随笔是 C++ Primer 5th ed. pp.39-40的摘录）Some characters, such as backspace or control characters, have no visible image. Such characters are non printab...
分类：
其他好文 时间：
2015-11-27 00:57:02
阅读次数：
171
C. Marina and VasyaMarina loves strings of the same length and Vasya loves when there is a third string, different from them in exactly t characters. ...
分类：
其他好文 时间：
2015-11-27 00:41:56
阅读次数：
236
All DNA is composed of a series of nucleotides abbreviated as A, C, G, and T, for example: "ACGAATTCCG". When studying DNA, it is sometimes useful to ...
分类：
其他好文 时间：
2015-11-25 22:00:00
阅读次数：
129
问题描述：Given 2 sequences, X = x1,...,xm and Y = y1,...,yn, find a common subsequence whose length is maximum. Subsequence need not be consecutive, but m...
分类：
编程语言 时间：
2015-11-23 13:13:45
阅读次数：
207
