【容斥原理】 HDOJ 4135 Co-prime

先提取出质因子，然后根据容斥的奇加偶减就行了。。。

#include <iostream>  
#include <queue>  
#include <stack>  
#include <map>  
#include <set>  
#include <bitset>  
#include <cstdio>  
#include <algorithm>  
#include <cstring>  
#include <climits>  
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 1000005
#define maxm 3000005
#define eps 1e-10
#define mod 998244353
#define INF 999999999
#define lowbit(x) (x&(-x))
#define mp mark_pair
#define ls o<<1
#define rs o<<1 | 1
#define lson o<<1, L, mid  
#define rson o<<1 | 1, mid+1, R
//#define debug(x) printf("AA x = %d BB\n", x);
//#pragma comment (linker,"/STACK:102400000,102400000")
typedef long long LL;
//typedef int LL;
using namespace std;
LL powmod(LL _a, LL _b){LL _res=1,_base=_a;while(_b){if(_b%2)_res=_res*_base%mod;_base=_base*_base%mod;_b/=2;}return _res;}
void scanf(LL &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='\n')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();}
// head

LL p[maxn];
LL ans, a, b, n, cnt;

void dfs(int pos, int dep, LL now, int flag)
{
	if(pos == dep) {
		ans += (b/now - (a-1)/now) * flag;
		return;
	}
	dfs(pos+1, dep, now, flag);
	dfs(pos+1, dep, now*p[pos], -flag);
}
void work(int __)
{
	ans = cnt = 0;
	for(int i = 2; i * i <= n; i++)
		if(n%i == 0) {
			p[cnt++] = i;
			while(n%i == 0) n/=i;
		}
	if(n > 1) p[cnt++] = n;
	dfs(0, cnt, (LL)1, 1);
	printf("Case #%d: %I64d\n", __, ans);
}
int main(void)
{
	int _, __;
	while(scanf("%d", &_)!=EOF) {
		__ = 0;
		while(_--) {
			scanf("%I64d%I64d%I64d", &a, &b, &n);
			work(++__);
		}
	}
	return 0;
}