poj 3090 Visible Lattice Points

 

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#include<iostream> #include<algorithm> using namespace std;  const int M=1e6;  int vis[M+4],P[M+4],cnt;  int fi[M+4];     void shai(int top){     cnt=0;     fi[1]=1;     for(int i=2;i<=top;i++){         if(vis[i]==0){             P[++cnt]=i;             fi[i]=i-1;          }         for(int j=1;j<=cnt&&i*P[j]<=top;j++){             vis[i*P[j]]=1;             if(i%P[j]==0){                 fi[i*P[j]]=fi[i]*P[j];                 break;              }             else             fi[i*P[j]]=fi[i]*(P[j]-1);          }      }  }  int sum[M+4];  int main(){     shai(1e6);     for(int i=1;i<=1e6;i++)      sum[i]=sum[i-1]+fi[i];           int tes,cas=0;cin>>tes;     while(tes--){         int x;         cin>>x;         cout<<++cas<<' '<<x<<' '<<2*sum[x]+1<<endl;      }  }