BZOJ1853: [Scoi2010]幸运数字

 1 #include<iostream>
 2 #include<algorithm>
 3 #include<cstdio>
 4 #include<cstring>
 5 #include<cmath>
 6 #include<cstdlib>
 7 using namespace std;
 8 typedef long long ll;
 9 typedef long double ld;
10 typedef pair<int,int> pr;
11 const double pi=acos(-1);
12 #define rep(i,a,n) for(int i=a;i<=n;i++)
13 #define per(i,n,a) for(int i=n;i>=a;i--)
14 #define Rep(i,u) for(int i=head[u];i;i=Next[i])
15 #define clr(a) memset(a,0,sizeof a)
16 #define pb push_back
17 #define mp make_pair
18 #define fi first
19 #define sc second
20 ld eps=1e-9;
21 ll pp=1000000007;
22 ll mo(ll a,ll pp){if(a>=0 && a<pp)return a;a%=pp;if(a<0)a+=pp;return a;}
23 ll powmod(ll a,ll b,ll pp){ll ans=1;for(;b;b>>=1,a=mo(a*a,pp))if(b&1)ans=mo(ans*a,pp);return ans;}
24 ll read(){
25 ll ans=0;
26 char last=‘ ‘,ch=getchar();
27 while(ch<‘0‘ || ch>‘9‘)last=ch,ch=getchar();
28 while(ch>=‘0‘ && ch<=‘9‘)ans=ans*10+ch-‘0‘,ch=getchar();
29 if(last==‘-‘)ans=-ans;
30 return ans;
31 }
32 //head
33 int n,m;
34 ll a[5000],b[5000],ans,l,r;
35 void dfs1(ll x){
36     if (x>r) return;
37     if (x)a[++n]=x;
38     dfs1(x*10+6);
39     dfs1(x*10+8);
40 }
41 void dfs2(int k,ll x,int kk){
42     if (k==m+1){
43         if (x==1) return;
44         ans+=(r/x-(l-1)/x)*kk;
45         return;
46     }
47     dfs2(k+1,x,kk);
48     ll y=b[k];
49     ll t=__gcd(y,x);
50     if ((long double)x/t<=(long double)r/y)dfs2(k+1,x/t*y,kk*(-1));
51 }
52 int main()
53 {
54     l=read(),r=read();
55       dfs1(0);
56       sort(a+1,a+n+1);
57       for (int i=1;i<=n;i++){
58           int pf=0;
59           for (int j=1;j<=i-1;j++)
60             if (a[i]%a[j]==0)pf=1;
61           if(!pf)b[++m]=a[i]; 
62       }
63     for (int i=1;i<=m/2;i++)swap(b[i],b[m+1-i]);
64     dfs2(1,1,-1);
65     cout<<ans<<endl;
66     return 0;
67 }