Counting Numbers - DP

#include <bits/stdc++.h>
#define task "TESTCODE"
using namespace std;
long long f[19][10][2][2];
long long a, b;
string s;
long long Count(int i, int bef, bool zeros, bool low)
{
    if (i == s.length())
    {
        return 1;
    }
    long long &res = f[i][bef][zeros][low];
    if (res != -1)
    {
        return res;
    }
    res = 0;
    int lim = s[i] - '0';
    if (low)
    {
        lim = 9;
    }
    for (int j = 0; j <= lim; ++ j)
    {
        if (j != bef || zeros == 0)
        {
            res += Count(i + 1, j, zeros | j, low | (j < s[i] - '0'));
        }
    }
    return res;
}
long long Get(long long x)
{
    s = to_string(x);
    memset(f, -1, sizeof(f));
    return Count(0,0,0,0);
}
void read()
{
   cin >> a >> b;
}
void solve()
{
   cout << Get(b) - Get(a - 1);
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    //freopen(task".INP", "r", stdin);
    //freopen(task".OUT", "w", stdout);
    int t = 1;
    bool typetest =false;
    if (typetest)
    {
        cin >> t;
    }
    for (int _ = 1; _ <= t; ++ _ )
    {
        read();
        solve();
    }
    return 0;
}