BZOJ-1853: [Scoi2010]幸运数字 (容斥原理)

 1 #include "bits/stdc++.h"
 2 using namespace std;
 3 typedef long long LL;
 4 const int MAX=3005;
 5 LL l,r,a[MAX],b[MAX],ans;
 6 bool p[MAX];
 7 void get(LL x){
 8     if (x>r) return;
 9     if (x) a[++a[0]]=x;
10     get(x*10+6),get(x*10+8);
11 }
12 LL gcd(LL x,LL y){return y==0?x:gcd(y,x%y);}
13 void dfs(LL x,LL y,LL lcm){
14     if (x>b[0]){
15         if (y&1) ans+=r/lcm-(l-1)/lcm;
16         else if (y) ans-=r/lcm-(l-1)/lcm;
17         return;
18     }
19     dfs(x+1,y,lcm);
20     LL g=gcd(b[x],lcm);
21     lcm/=g;
22     if (r/lcm<b[x]) return;
23     lcm*=b[x];
24     dfs(x+1,y+1,lcm);
25 }
26 int main(){
27     freopen ("lucky.in","r",stdin);freopen ("lucky.out","w",stdout);
28     int i,j;
29     scanf("%lld%lld",&l,&r);
30     get(0);sort(a+1,a+a[0]+1);
31     for (i=1;i<=a[0];i++)
32         if (!p[i]){
33             b[++b[0]]=a[i];
34             for (j=i+1;j<=a[0];j++) if (a[j]%a[i]==0) p[j]=true;
35         }
36     for (i=1;i<=b[0]/2;i++) swap(b[i],b[b[0]-i+1]);
37     dfs(1,0,1);
38     printf("%lld",ans);
39     return 0;
40 }