AcWing 311. 月之谜 数位dp

#include<iostream>
#include<cstring>
#include<cstdio> 
#include<algorithm>
using namespace std;
#define int long long
typedef long long ll;
const int N=200;
int read()
{
    int res=0,ch,flag=0;
    if((ch=getchar())=='-')             //判断正负
        flag=1;
    else if(ch>='0'&&ch<='9')           //得到完整的数
        res=ch-'0';
    while((ch=getchar())>='0'&&ch<='9')
        res=res*10+ch-'0';
    return flag?-res:res;
}
int mod;
int l,r,a[N],dp[N][N][N];
int dfs(int pos,int sum,int now,int limit)
{
    if(!pos)
        return (sum==mod)&&(now==0);
    if(!limit&&dp[pos][sum][now]!=-1)
        return dp[pos][sum][now];
    int up=limit?a[pos]:9;
    int res=0;
    for(int i=0;i<=up;i++)
        res+=dfs(pos-1,sum+i,(now*10+i)%mod,limit&&i==up);
    if(!limit)
        dp[pos][sum][now]=res;
    return res;
}
int solve(int x)
{
    memset(a,0,sizeof a);
    memset(dp,-1,sizeof dp);
    int cnt=0;
    while(x)
    {
        a[++cnt]=x%10;
        x/=10;
    }
    int res=0;
    //枚举各位数字的和 
    for(mod=1;mod<=cnt*9;mod++)
    {
        memset(dp,-1,sizeof dp);
        res+=dfs(cnt,0,0,1);
    }
    return res;
}
signed main()
{
    l=read(),r=read();
    cout<<solve(r)-solve(l-1)<<endl;
    return 0; 
}