Codeforces 595B

595B - Pasha and Phone

代码：

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
const int N=1e5+5;
const int INF=0x3f3f3f3f;
const int MOD=1e9+7;
ll a[N];
int b[N];
int dp[11]={1};
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n,k;
    cin>>n>>k;
    for(int i=0;i<n/k;i++)cin>>a[i];
    for(int i=0;i<n/k;i++)cin>>b[i];
    for(int i=1;i<=k;i++)dp[i]=dp[i-1]*10;

    ll ans=1;
    for(int i=0;i<n/k;i++)
    {
        int t=0;
        ll n1=(dp[k]-1)/a[i]+1;//a[i]倍数的数量 
        ll n2=(dp[k-1]-1)/a[i]+1;//最高位为0的a[i]倍数的数量 
        ll n3=(dp[k-1]*(b[i]+1)-1)/a[i]-(dp[k-1]*b[i]-1)/a[i];//最高位为b[i]的a[i]的倍数的数量 
        if(b[i]==0)ans*=n1-n2;
        else ans*=n1-n3;
        ans%=MOD;
    }
    cout<<ans<<endl;
    return 0;
}