HDU 4135

容斥原理简单应用

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#define LL __int64
#define Np 100000
using namespace std;

bool isprime[Np];
LL prime[Np],np;
LL fac[100],fp;

void initial(){
	np=0;
	memset(isprime,true,sizeof(isprime));
	for(LL i=2;i<Np;i++){
		if(isprime[i]){
			prime[np++]=(LL)i;
			for(LL j=i*i;j<Np;j+=i)
			isprime[j]=false;
		}
	}
}

void dfs(LL i,LL num, LL p,LL s,LL &ans,LL n){
	if(i>=n){
		if(num==0){
			ans=s;
		}
		else if(num&1){
			ans-=s/p;
		}
		else ans+=s/p;
		return ;
	}
	dfs(i+1,num,p,s,ans,n);
	dfs(i+1,num+1,p*fac[i],s,ans,n);
}

LL  work(LL a,LL b,LL n){
	LL p=n;
	fp=0;
	for(LL i=0;i<np&&prime[i]*prime[i]<=p;i++){
		if(p%prime[i]==0){
			fac[fp++]=prime[i];
			while(p%prime[i]==0)
			p/=prime[i];
		}
	}
	if(p>1) fac[fp++]=p;
	
	LL ansA,ansB;
	ansA=ansB=0;
	
	dfs(0,0,1,a-1,ansA,fp);
	dfs(0,0,1,b,ansB,fp);
	
	return ansB-ansA;
}

int main(){
	int T,kase=0; 
	LL a,b,n;
	initial();
	scanf("%d",&T);
	while(T--){
		scanf("%I64d%I64d%I64d",&a,&b,&n);
		LL ans=work(a,b,n);
		printf("Case #%d: %I64d
",++kase,ans);
	}
	return 0;
}