bzoj1853: [Scoi2010]幸运数字

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
typedef long long LL;
const int maxn = 30000 + 10;

LL a,b,cnt,n;
LL lucky[maxn];
bool flag[maxn];


void build(LL n) {
    if(n>b) return;
    if(n) lucky[++cnt]=n;
    build(n*10+6);
    build(n*10+8);    
}

bool cmp(LL a,LL b) {
    return a>b;    
}

void predo() {
    cnt=n=0;
    build(0);    
    sort(lucky+1,lucky+cnt+1,cmp);
    
    for(int i=1;i<=cnt;i++) {
        flag[i]=true;
        for(int j=cnt;j>i;j--) if(lucky[i]%lucky[j]==0) flag[i]=false;
    }
    
    for(int i=1;i<=cnt;i++) if(flag[i]) lucky[++n]=lucky[i];
}

LL gcd(LL a,LL b) {
    return b==0?a:gcd(b,a%b);    
}

LL dfs(int dep,LL cur) {
    //printf("%d %lld\n",dep,cur);
    if(dep>n) return b/cur-a/cur;
    LL res=dfs(dep+1,cur),g=gcd(cur,lucky[dep]);
    if(cur/g<=b/lucky[dep]) 
        res-=dfs(dep+1,cur/g*lucky[dep]);
    return res;
}


int main() {
    scanf("%lld%lld",&a,&b);
    a--;
    predo();    
    printf("%lld\n",b-a-dfs(1,1));
    return 0;
}