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;Set ASo we only need to enumerate each prime, each number (here can be used to maintain the prefix of N, recorded as F[n]) to solve the ans=σf[n/prime[i]]*2-1 (consider a>b, and subtract values such as ().#include Const intmaxn=10000010;BOOLPD[MAXN];Long LongPhi[maxn],prime[maxn],top,n,ans;voidES () { for(intI=2; i){ if(!Pd[i]) {prime[++top]=i; Phi[i]=i-1; } for(intj=1; j) {Pd[prime[j]*i]=1; if(i%prime[j]==0) {Phi[prime[j]*i]=phi[i]*Prime[j]; Break; } Phi[prime[j]*i]=phi[i]* (pr

Yesterday 18 Preliminaries today (⊙o⊙)I've decided to do a good job of documenting the issues.Although not much of a relationship, always feel that this can be regarded as a node, can be a slight change of opportunitySo... For the last simulation of the T1 so simple law has not found this, today did some number theory (especially to find the law) topichttps://www.luogu.org/problemnew/show/P2158Title DescriptionAs a sports Commissioner, C June is responsible for the training of the

The upper triangle line is exactly the Euler function of [1,n-1]Http://www.luogu.org/problem/show?pid=2158#sub1 //#pragma COMMENT (linker, "/stack:167772160")2#include 3#include 4#include 5#include 6#include 7#include 8#include 9#include Set>Ten#include One#include A#include -#include - //#include the using namespacestd; - #defineCLC (A, B) memset (A,b,sizeof (a)) - #defineLL Long Long - voidfre () { +Freopen ("In.txt","R", stdin); - } + Const intINF =0x3f3f3f3f; A #defineEPS 1e-8 at //cons

Euler sieve template problem#include This is OK ~ ~ ~"Bzoj 2190" "Sdoi 2008" guard of Honor Euler sieve

"Topic link"http://www.lydsy.com/JudgeOnline/problem.php?id=2190Test instructionsN*n Square, the number of squares that can be seen in the (0,0) lattice.IdeasPreprocessing the Euler function.(x, y) the =1,1Of course, you can use Möbius inversion, too lazy to write (? ￣ ￣)?Code1#include 2#include 3#include 4 using namespacestd;5 6 Const intN = 5e4+Ten;7 8 intN;9 intPhi[n];Ten One voidGet_phi (intN) A { -phi[1]=1; - for(intI=2; iif(!Phi[i]) the { - for(intj=i;ji) - { -

1#include 2#include 3#include 4 #defineM 400055 using namespacestd;6 intAns,n,phi[m],q[m],tot,f[m];7 intMain ()8 {9scanf"%d",n);Tenphi[1]=1; One for(intI=2; i) A { - if(!F[i]) - { thetot++; -q[tot]=i; -phi[i]=i-1; - } + for(intj=1; j) - { + if(q[j]*i>N) A Break; atf[q[j]*i]=1; - if(i%Q[j]) -phi[i*q[j]]=phi[i]* (q[j]-1); - Else -phi[i*q[j]]=phi[i]*Q[j]; - } in } - fo

Title Effect: There is a grid component diagram, assuming that three people in a straight line, then the first person will not see a third person. Now, there is a man standing in the. I asked him if he could see the matrix of the number of n*n.Think: If you want to stand (in the first place) This man sees a position (x, y) of a person. GCD (x, y) = = 1, which is a classic model, only requires a PHI within N and is able to.The method is linear sieve.CODE:#include Copyright notice: This article B

Arithmetical...The answer is the sum of the first n-1 Euler functions and then *2+1#include BZOJ-2190 [SDOI2008] honor Guard