B - Calculation 2
Given a positive integer N, your task is to calculate the sum of the positive integers less than N which are not coprime to N. A is said to be coprime to B if A, B share no common positive divisors except 1.
Input
For each test case, there is a line containing a positive integer N(1 ≤ N ≤ 1000000000). A line containing a single 0 follows the last test case.
Output
For each test case, you should print the sum module 1000000007 in a line.
Sample Input
3
4
0
Sample Output
0
2
用个互斥原理就可以了
#include<iostream>
#include<stdio.h>
#include<stdlib.h>
#include<cmath>
#include<string.h>
#include<algorithm>
#define sf scanf
#define pf printf
//#define cl clear()
#define pb push_back
#define mm(a,b) memset((a),(b),sizeof(a))
#include<vector>
typedef __int64 ll;
typedef long double ld;
const ll mod=1e9+7;
using namespace std;
vector< int >v;
const double pi=acos(-1.0);
ll cal(ll x,ll n)
{
if(x==n) return 0;
int a=(n-1)/x;
return (x*a+(x*a*(a-1))/2)%mod;
}
ll solve(ll n)
{
ll x=n;
for(int i=2;i*i<=x;i++)
{
// cout<<"1"<<endl;
if(x%i==0)
{
v.pb(i);
while(x%i==0)
{
x/=i;
}
}
}
if(x>1) v.pb(x);
ll sum=0;
for(int i=1;i<(1<<v.size()) ;i++)
{
ll bits=0,ans=1;
for(int j=0;j<v.size() ;j++)
{
if((1<<j)&i)
{
bits++;
ans*=v[j];
}
}
if(bits&1)
sum=(sum+cal(ans,n))%mod;
else
{
sum=(sum-cal(ans,n));
while(sum<0)
sum+=mod;
}
}
return sum;
}
int main()
{
// freopen("output1.txt", "r", stdin);
ll n;
while(1)
{
v.clear();
sf("%I64d",&n);
if(n==0) return 0;
pf("%I64d\n",solve(n));
}
}