[BZOJ2226][Spoj 5971] LCMSum Description Given n, calculate the sum LCM(1,n) + LCM(2,n) + .. + LCM(n,n), where LCM(i,n) denotes the Least Common Multiple of the integers i and n. Input The first line contains T the number of test cases. Each of the n
题意:给定整数N,求1<=x,y<=N且Gcd(x,y)为素数的数对(x,y)有多少对 1<=N<=10^7 思路:莫比乌斯反演,同BZOJ2820…… ; ..max]of int64; prime,flag,f,mu:..max]of longint; n,m,i,j,t,v,cas:longint; function clac(n:longint):int64; var x,i,pos:longint; begin clac:=; i:=; while i<=n do
题目地址:light oj 1007 第一发欧拉函数. 欧拉函数重要性质: 设a为N的质因数.若(N % a == 0 && (N / a) % a == 0) 则有E(N)=E(N / a) * a:若(N % a == 0 && (N / a) % a != 0) 则有:E(N) = E(N / a) * (a - 1) 对于这题来说.首先卡MLE.. 仅仅能开一个数组..所以把前缀和也存到欧拉数组里. 然后卡long long. .要用unsigned long lo