hdu 4135 Co-prime（容斥原理，质因数分解）

这个思路还是很巧妙的（其实就是转化为二进制，不知道是不是板子，收藏一下）

#include <set>
#include <map>
#include <queue>
#include <stack>
#include <math.h>
#include <vector>
#include <string>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <iostream>
#include <algorithm>
#define zero(a) fabs(a)<eps
#define lowbit(x) (x&(-x))
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
#define MOD 1000000007
int max(int x,int y){return x>y?x:y;};
int min(int x,int y){return x<y?x:y;};
int max(int x,int y,int z){return max(x,max(y,z));};
int min(int x,int y,int z){return min(x,min(y,z));};
typedef long long LL;
const double PI=acos(-1.0);
const double eps=1e-8;
const int inf=0x3f3f3f3f;
const LL linf=0x3f3f3f3f3f3f3f3fLL;
using namespace std;
int read()
{
    int x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}

int prime[33],pn;
LL calc(LL n)
{
    LL res=0;
    for(int i=1;i<(1<<pn);i++){
        int tmp=1,cnt=0;
        for(int j=0;j<pn;j++){
            if(((i>>j)&1)==0)continue;
            ++cnt;
            tmp*=prime[j];
        }
        if(cnt&1)res+=n/tmp;
        else res-=n/tmp;
    }
    return n-res;
}
int main()
{
    LL a,b;
    int T,n;
    scanf("%d",&T);
    int cas=1;
    while(T--){
        scanf("%lld%lld%d",&a,&b,&n);
        pn=0;
        for(int i=2;i*i<=n;i++){
            if(n%i)continue;
            while(n%i==0)n/=i;
            prime[pn++]=i;
        }
        if(n!=1)prime[pn++]=n;
        printf("Case #%d: %lld
",cas++,calc(b)-calc(a-1));
    }
}