题意 给定闭区间[l,r] [l,r] [l,r],找出区间内满足t=a2+b2 t=a^{2}+b^{2} t=a2+b2的所有素数t t t的个数( a,b a,b a,b为任意正整数). 思路 这是一个手推很容易找出规律的数学题 听说是传说中的 费马二平方定理 除2以外的所有的素数都可以分为两类:4k + 1,4k + 3 4k + 1可以表示为2个整数的平方和,但4k + 3不行 (上面来自题解) 这道题只要判断一个质数就够了吧?%4==1符合要求 因为一开始MLE了,看了一下题解,用的…

2790. Double Happiness   time limit per test 3 seconds memory limit per test 128 megabytes input standard input output standard output On the math lesson a teacher asked each pupil to come up with his own lucky numbers. As a fan of number theory Pete…

Double Happiness On the math lesson a teacher asked each pupil to come up with his own lucky numbers. As a fan of number theory Peter chose prime numbers. Bob was more original. He said that number t is his lucky number, if it can be represented as:t…

首先要在 face++ 注册一个账号,并且创建一个应用,拿到 api key 和 api secret: 下载 java 接入工具,一个 jar 包:https://github.com/FacePlusPlus/java-sdk 请求返回的数据是 json 格式,需要导入 json 解析包: commons-beanutils-1.8.3.jar commons-lang-2.5.jar commons-collections-3.2.2.jar ezmorph-1.0.6.jar json-…

题目链接 C. Double Happiness time limit per test 5 seconds memory limit per test 128 megabytes input standard input output standard output On the math lesson a teacher asked each pupil to come up with his own lucky numbers. As a fan of number theory Pete…

http://acm.hdu.edu.cn/showproblem.php?pid=5072 题意:给出N个数,求有多少个三元组,满足三个数全部两两互质或全部两两不互质. 题解: http://dtyfc.com/acm/980 我看的这个学会的…… 可以先求不满足要求的三元组数量,也就是abc,a和b互质,b和c不互质. 这样就要找这n个数中,和某个数不互质的数的个数. 可以质因数分解+容斥原理,求出和某个数不互质的数的个数(也就是和这个数有相同因数的数的个数). 还要先预处理以某个数x为因子…

题目:An Easy Problem! 题意:求给出数的最小进制. 思路:暴力WA: discuss中的idea: 给出数ABCD,若存在n 满足 (A* n^3 +B*n^2+C*n^1+D*n^0)%(n-1) == 0 则((A* n^3)%(n-1) +(B*n^2)%(n-1)+(C*n^1)%(n-1)+D%(n-1))%(n-1) == 0             (A+B+C+D)%(n-1) == 0 NB! 是时候深入的看下数论了: 模运算法则: 模运算与基本四则运算有些相似…

Lucas的数论 reference 题目在这里> < Pre 数论分块 默认向下取整时. 形如\(\sum\limits_{i=1}^n f\left( \frac{n}{i}\right)\)的求和,由于\(\frac{n}{r}\)的值只有\(\sqrt{n}\)个,可以直接数论分块上. 题解 记原式为\(S(n)\),有 \[S(n)=\sum_{i\rightarrow n}\sum_{j\rightarrow n}[\gcd{i,j}=1]\frac{n}{i}\frac{n}{j…

Description Prof. Kaykobad has given Nasa the duty of buying some food for the ACM contestents. Nasa decided to buy n different items. He then asked each of the mcontestents how much of each item they want to eat. They could not give any logical answ…

题意:三个数x, y, z. 给出最大公倍数g和最小公约数l.求满足条件的x,y,z有多少组. 题解:设n=g/l n=p1^n1*p2^n2...pn^nk (分解质因数 那么x = p1^x1 * p2^x2 * .... ^ pn^xk y = p1^y1 * p2^y2 * .... ^ pn^yk x = p1^z1 * p2^z2 * .... ^ pn^zk 那么对于任意i (0<=i<=k) 都有 min(xi, yi, zi) = 0, max(xi, yi, zi) = n…