BZOJ 4421 Digit Division

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define maxn 300050
#define maxm 1000050
#define mod 1000000007
using namespace std;
long long n,m,t[maxn],sum[maxm],dp[maxn];
char s[maxn];
int main()
{
    scanf("%lld%lld",&n,&m);
    scanf("%s",s);
    dp[0]=sum[0]=1;
    for (long long i=1;i<=n;i++)
        t[i]=(t[i-1]*10+s[i-1]-‘0‘)%m;
    for (long long i=1;i<=n;i++)
    {
        dp[i]=sum[t[i]];
        sum[t[i]]=(sum[t[i]]*2)%mod;
    }
    printf("%lld\n",dp[n]%mod);
    return 0;
}