题目链接:http://codeforces.com/gym/101775/problem/A It is said that a dormitory with 6 persons has 7 chat groups ^_^. But the number can be even larger: since every 3 or more persons could make a chat group, there can be 42 different chat groups. Given N…

It is said that a dormitory with 6 persons has 7 chat groups ^_^. But the number can be even larger: since every 3 or more persons could make a chat group, there can be 42 different chat groups. Given N persons in a dormitory, and every K or more per…

传送门:http://acm.hdu.edu.cn/showproblem.php?pid=6467 简单数学题 Time Limit: 4000/2000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 308    Accepted Submission(s): 150 Problem Description 已知 F(n)=∑i=1n(i×∑j=inCij) 求 F(n) m…

简单数学题 Time Limit: 4000/2000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 580    Accepted Submission(s): 257 Problem Description 已知 F(n)=∑i=1n(i×∑j=inCij) 求 F(n) mod 1000000007   Input 多组输入,每组输入占一行,包含一个整数n(1 <= n <…

Discrete Function There is a discrete function. It is specified for integer arguments from 1 to N (2 ≤ N ≤ 100000). Each value of the function is longint (signed long in C++). You have to find such two points of the function for which all points betw…

5773. [NOIP2008模拟]简单数学题 (File IO): input:math.in output:math.out Time Limits: 1000 ms  Memory Limits: 262144 KB  Detailed Limits   Goto ProblemSet Description       话说, 小X是个数学大佬,他喜欢做数学题.有一天,小X想考一考小Y.他问了小Y一道数学题.题目如下:      对于一个正整数N,存在一个正整数T(0<T<N),使得…

传送门:Chat Group(gym101775A) 题意:一个宿舍中又n个人,最少k(k >= 3)个人就可以建一个讨论组,问最多可以建多少个不同的讨论组. 思路:求组合数的和,因为涉及除法取余,所以要求逆元来解题. 虽然之前看到过有关逆元的知识,但是一直没有弄明白逆元的应用.嗯~~挖下的坑终于把自己给坑了.这次认栽!! 最终的结果是:C(n,k)+C(n,k+1)+.......+C(n,n) = 2^n - ( C(n,0) + C(n,1) + C(n,2) + ......+C(n,k…

Description       话说, 小X是个数学大佬,他喜欢做数学题.有一天,小X想考一考小Y.他问了小Y一道数学题.题目如下:      对于一个正整数N,存在一个正整数T(0<T<N),使得…

题目链接:https://codeforces.com/gym/102056/problem/I Warm sunshine, cool wind and a fine day, while the girl watching is pursuing in chaos. Rikka reached out her hand and got the garland on her head, finding LCR with the immortal smile. The dream ended u…

题目链接:https://cn.vjudge.net/contest/274151#problem/A 具体思路:我们可以先把所有的情况算出来,为2^n.然后不合法的情况减去就可以了.注意除法的时候要用到逆元. AC代码: #include<iostream> #include<cstring> #include<cmath> #include<algorithm> #include<stdio.h> #include<queue>…