【题解】AHOI2009同类分布

#include 
using namespace std;
#define int long long
int a[20], Res, mul[20];
int f[20][165][165][2];

int read()
{
    int x = 0, k = 1;
    char c;
    c = getchar();
    while(c <'0' || c > '9') { if(c == '-') k = -1; c = getchar(); }
    while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
    return x * k;
}

#define Pre f[now][tot][rm][lim]
int DP(int now, int tot, int rm, bool lim)
{
    if(~Pre) return Pre;
    else Pre = 0;
    if(tot > now * 9) return 0;
    if(now == 1) 
    {
        if(tot > 9 || (tot > a[now] && lim)) return Pre = 0;
        return Pre = ((Pre = tot % Res == rm) ? 1 : 0);
    }
    for(int i = 0; i <= 9; i ++)
    {
        if(i > a[now] && lim) break;
        if(tot break;
        int q = (mul[now] * i) % Res; q = q % Res; 
        int L = (i == a[now] && lim);
        f[now][tot][rm][lim] += DP(now - 1, tot - i, (rm - q + Res) % Res, L);
    }
    return f[now][tot][rm][lim];
}
#undef Pre

int Solve(int x)
{
    int k = x, ans = 0, num = 0; 
    while(k) num ++, a[num] = k % 10, k /= 10;
    for(int i = 1; i <= 163; i ++)
    {
        Res = i; if(i > num * 9) continue;
        memset(f, -1, sizeof(f));
        ans += DP(num, i, 0, 1);
    }
    return ans;
}

signed main()
{
    int a = read(), b = read(); mul[1] = 1;
    for(int i = 2; i <= 20; i ++) mul[i] = mul[i - 1] * 10;
    printf("%lld\n", Solve(b) - Solve(a - 1));
    return 0;
}