Create 1190.cpp

51nod/1190.cpp

@@ -0,0 +1,117 @@
+/*************************************************************************
+    > File Name: 1190.cpp
+    > Author: kelvin
+    > Mail: [email protected] 
+    > Created Time: 2016年04月28日 星期四 17时39分16秒
+    反演
+ ************************************************************************/
+
+#include<bits/stdc++.h>
+using namespace std;
+#define REP(i,a,b)	for(int i=a;i<b;++i)
+#define LL		long long
+#define mset(a,b)	memset(a,b,sizeof a)
+#define scan(n)	scanf("%d",&n)
+const int maxn = 1000006;
+const int mod = 1000000007;
+
+int fac[33],num[33],cnt;
+int prime[maxn];
+void getP()
+{
+	REP(i,2,maxn)
+	{
+		if(!prime[i])	prime[++prime[0]]=i;
+		for(int j=1;j<=prime[0] && prime[j]<=maxn/i;++j)
+		{
+			prime[i*prime[j]]=1;
+			if(i%prime[j]==0)	break;
+		}
+	}
+}
+
+void div(int b)
+{
+	cnt=0;							
+	int x=b;
+	REP(i,1,prime[0]+1)
+	{
+		LL p=prime[i];
+		if(p*p>x)	break;
+		if(x%p)	continue;
+		fac[cnt]=p;
+		num[cnt]=0;
+		while(x%p==0)
+		{
+			x/=p;
+			num[cnt]++;
+		}
+		cnt++;
+	}
+	if(x!=1)
+	{
+		fac[cnt]=x;
+		num[cnt++]=1;
+	}
+}
+LL a,b;
+inline void init()
+{
+	div(b);
+}
+inline LL up(int x,int y)
+{
+	return (x-1)/y+1;
+}
+LL getans(int d,LL mu)
+{
+	LL ret=1;
+	LL x=up(a,d);
+	LL y=b/d-x+1;
+	x+=b/d;
+	ret=x*y/2%mod;
+	ret=ret*mu%mod;
+	if(ret<0)	ret+=mod;
+	return	ret; 
+}
+
+LL ans;
+void dfs(int cur,int dep,LL mu)
+{
+	if(dep==cnt)
+	{
+		ans+=getans(cur,mu);
+		ans%=mod;
+		return ;
+	}
+
+	REP(i,0,num[dep]+1)
+	{
+		dfs(cur,dep+1,mu);
+		cur*=fac[dep];
+		if(!i)	mu=mu*(1-fac[dep])%mod;
+	}
+}
+
+
+int main()
+{
+	//freopen("1190.in","r",stdin);
+	//freopen("1190.out","w",stdout);
+	getP();
+	int t;
+	scan(t);
+	while(t--)
+	{
+		scanf("%lld%lld",&a,&b);
+		init();
+		ans=0;
+		dfs(1,0,1);
+		ans=ans*b%mod;
+		if(ans<0)	ans+=mod;
+		printf("%lld\n",ans);
+
+	}
+
+    return 0;
+}