Bzoj 2818 gcd (Möbius inversion)

GcdTime limit:10000MS Memory Limit:262144KB 64bit IO Format:%lld &%llu SubmitStatus

Description

Given an integer n, 1<=x,y<=n and gcd (x, y) are prime
Number pairs (x, y) how many pairs.

Input

An integer n

Output

Title

Sample Input

4

Sample Output

4

#include <cstdio> #include <algorithm> #include <iostream> #include <cmath> #include < Cstring> #include <vector> #define LL long long#define N 10000010using namespace Std;bool check[n+10];int prime[n    ];int mu[n+10];int tot;int n;void moblus () {memset (check,0,sizeof check);    Mu[1]=1;    tot=0;            for (int i=2; i<n; i++) {if (!check[i]) {prime[tot++]=i;        Mu[i]=-1;            } for (int j=0; j<tot; J + +) {if (i*prime[j]>n) break;            Check[i*prime[j]]=1;                if (i%prime[j]==0) {mu[i*prime[j]]=0;            Break        } else mu[i*prime[j]]=-mu[i];    }}}int Main () {moblus ();        while (scanf ("%d", &n)!=eof) {ll ans=0;            for (int i=0; i<tot; i++) {int x=n/prime[i];            if (x==0) break;        for (int j=1; j<=x; j + +) ans+= (LL) mu[j]* (x/j) * (x/j);    } printf ("%lld\n", ans); } return 0;} 

Bzoj 2818 gcd (Möbius inversion)