[AHOI 2009] 同类分布

[题目链接]

          https://www.lydsy.com/JudgeOnline/problem.php?id=1799

[算法]

        数位DP

[代码]

        

#include<bits/stdc++.h>
using namespace std;
const int MAXS = 162;

int i;
long long a,b,ans;
long long f[20][MAXS + 5][MAXS + 5][2];

inline long long calc(long long x,int p)
{
        int i,j,k,t,len;
        int a[20];
        len = 0;
        while (x > 0)
        {
                a[++len] = x % 10;
                x /= 10;
        }
        reverse(a + 1,a + len + 1);
        memset(f,0,sizeof(f));
        f[0][0][0][1] = 1;
        for (i = 0; i < len; i++)
        {
                for (j = 0; j <= p; j++)
                {
                        for (k = 0; k < p; k++)
                        {
                                if (!f[i][j][k][0] && !f[i][j][k][1]) continue;
                                for (t = 0; t <= 9; t++)
                                {
                                        if (j + t <= p) f[i + 1][j + t][(k * 10 + t) % p][0] += f[i][j][k][0];
                                        if (t < a[i + 1] && j + t <= p) f[i + 1][j + t][(k * 10 + t) % p][0] += f[i][j][k][1];
                                        if (t == a[i + 1] && j + t <= p) f[i + 1][j + t][(k * 10 + t) % p][1] += f[i][j][k][1];
                                }    
                        }    
                }    
        }    
        return f[len][p][0][0] + f[len][p][0][1]; 
}

int main() 
{
    
        scanf("%lld%lld",&a,&b);
        for (i = 1; i <= MAXS; i++) ans += calc(b,i) - calc(a - 1,i);
        printf("%lld\n",ans);    
        
        return 0;
}