HDU 1695（莫比乌斯之容斥）

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
typedef long long ll;

const int maxn=1000000+5;

int p[maxn];
int len;
int boo[maxn];
int su[maxn/2];
int nsu[maxn];
int no;
int a,b,c,d,k;
int sum;

void phi()
{
    p[1]=1;
    for(int i=2;i<maxn;i++){
        if(!p[i]){
            for(int j=i;j<maxn;j+=i){
                if(!p[j]) p[j]=j;
                p[j]=p[j]/i*(i-1);
            }
        }
    }
}

void quick_pri(){
    boo[0]=boo[1]=1;
    for(int i=2;i<maxn;i++){
        if(!boo[i]) su[len++]=i;
        for(int j=0;j<len&&su[j]*i<maxn;j++){
            boo[su[j]*i]=1;
            if(i%su[j]==0) break;
        }
    }
}

void dfs(int i,int nu,int x,int mu){
    if(nu==x){
        sum+=b/mu;
        return ;
    }if(i==no) return ;
    dfs(i+1,nu+1,x,mu*nsu[i]);
    dfs(i+1,nu,x,mu);
}

int rong(){
    int s=0;
    for(int i=1;i<=no;i++){
        sum=0;
        dfs(0,0,i,1);
        if(i&1) s+=sum;
        else s-=sum;
    }
    return b-s;
}

int main()
{
    phi();
    quick_pri();
    int t;
    int casei=1;
    cin>>t;
    while(t--){
        cin>>a>>b>>c>>d>>k;
        if(k==0){
            printf("Case %d: 0\n",casei++);continue;
        }
        b/=k,d/=k;
        if(b>d) swap(b,d);
        ll ans=0;
        for(int i=1;i<=b;i++) ans+=p[i];
        for(int i=b+1;i<=d;i++){
            no=0;
            a=i;
            for(int j=0;j<len&&su[j]*su[j]<=a;j++){
                if(!(a%su[j])){
                    nsu[no++]=su[j];
                    while(!(a%su[j])) a/=su[j];
                }
            }
            if(a>1) nsu[no++]=a;
            ans+=rong();
        }
        printf("Case %d: %lld\n",casei++,ans);
    }
    return 0;
}