Problem Description There are n people standing in a line. Each of them has a unique id number. Now the Ragnarok is coming. We should choose 3 people to defend the evil. As a group, the 3 people should be able to communicate. They are able to communi…

题意:给定区间和n,求区间中与n互素的数的个数, . 思路:利用容斥定理求得先求得区间与n互素的数的个数,设表示区间中与n互素的数的个数, 那么区间中与n互素的数的个数等于.详细分析见求指定区间内与n互素的数的个数 容斥原理 AC代码 #include <cstdio> #include <cmath> #include <cctype> #include <bitset> #include <algorithm> #include <cs…

<题目链接> 题目大意: 给定区间[A,B](1 <= A <= B <= 10 15)和N(1 <=N <= 10 9),求出该区间中与N互质的数的个数. 解题分析: 将求区间[A,B]与N互质的数转化成求[1,B] 区间与N互质的个数  -  [1,A-1]中与N互质的个数.同时,因为直接求区间内与N互质的数不好求,我们从反面入手,求出与N不互质的数,借鉴埃筛的思想,我们先求出N的所有质因子,然后将这些质因子在区间内倍数的个数全部求出(即与N不互质的数),再用…

Co-prime Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 2307    Accepted Submission(s): 861 Problem Description Given a number N, you are asked to count the number of integers between A and B…

Frogs Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 1315    Accepted Submission(s): 443 Problem Description There are m stones lying on a circle, and n frogs are jumping over them.The stones a…

给出n个数,给出m个询问,询问 区间[l,r] [u,v],在两个区间内分别取一个数,两个的和为k的对数数量. $k<=2*N$,$n <= 30000$ 发现可以容斥简化一个询问.一个询问的答案为 $[l,v]+(r,u)-[l,u)-(r,v]$,那么我们离线询问,将一个询问分成四个,分块暴力就行了. 然后就是注意细节,不要发生越界,访问错位置之类比较蠢的问题了. /** @Date : 2017-09-24 19:54:55 * @FileName: HDU 5213 分块 容斥.cpp…

求满足$1<=X<=N ,(X,N)>=M$的个数,其中$N, M (2<=N<=1000000000, 1<=M<=N)$. 首先,假定$(x, n)=m$,那么 $(\frac{x}{n},\frac{n}{m})=1$,故$$ans=\sum_{i=m}^{n}\varphi(\frac{n}{i})$$ ん?遅い! $$\sum_{i=m}^{n}\varphi(\frac{n}{i})=\sum\limits_{d|n}{\varphi(\frac{n}…

http://acm.hdu.edu.cn/showproblem.php?pid=5072 题意:给出 n 个互不相同的数,求满足以下条件的三元无序组的个数:要么两两互质要么两两不互质. 思路:根据同色三角形原理求,白书105页.求它不符合条件的情况数,先对每一个数分解质因子,然后利用容斥求出与这个数不互质的数的个数,那么不符合条件的的情况数加上(x-1)*(n-x);  x为其它数与这个数不互质的个数.最后总的情况数减去不符合的情况数,剩下的就是答案.再求多少个是这个数的倍数的时候,可以用筛…

GCD 题目连接: http://acm.hdu.edu.cn/showproblem.php?pid=1695 Description Given 5 integers: a, b, c, d, k, you're to find x in a...b, y in c...d that GCD(x, y) = k. GCD(x, y) means the greatest common divisor of x and y. Since the number of choices may be…

Frogs Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://acm.hdu.edu.cn/showproblem.php?pid=5514 Description There are m stones lying on a circle, and n frogs are jumping over them.The stones are numbered from 0 to m−1 and the frogs are numbered fro…