Maximum sum of digits count in range L to R

#include<bits/stdc++.h>
#define ll long long
#define endl '\n'
#define IOS ios::sync_with_stdio(0); cin.tie(0);
#define FIO freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout);
#define MOD 1000000007LL
//#define MOD 998244353LL
#define all(x) (x).begin(),(x).end()

using namespace std;

vector<vector<vector<ll>>> dp;

ll f(int rem, int i, string mx, bool isLess){ // This function counts total number of x, having sumOfDigits(x) == s in range 1 to mx
    if(rem < 0) return 0;
    if(rem == 0) return 1;
    if(i == mx.length()) return 0;

    if(dp[rem][i][isLess] != -1) return dp[rem][i][isLess];

    int d = mx[i] - '0';
    ll ret = 0;
    if(!isLess){ // We can choose digits from 0 to mx[i]
        for(int currD = 0; currD < d; currD++) ret += f(rem - currD, i + 1, mx, true);
        ret += f(rem - d, i + 1, mx, false);
    }
    else{ // We can choose any digit from 0 to 10
        for(int currD = 0; currD < 10; currD++) ret += f(rem - currD, i + 1, mx, true);
    }

    dp[rem][i][isLess] = ret;

    return ret;
}

void init(int s){
    dp.clear();
    dp.resize(s + 1, vector<vector<ll>> (20, vector<ll> (2, -1)));
}

int main(){
    #ifndef ONLINE_JUDGE
        FIO
    #endif
    IOS

    ll low, hi;
    cin >> low >> hi;

    ll sum = 0, maxCount = 0;

    for(int s = 1; s <= 162; s++){ // maximum sum can be 18 * 9 = 162.
        init(s);
        ll uptoHi = f(s, 0, to_string(hi), false);

        init(s);
        ll uptoLow = f(s, 0, to_string(low - 1), false);

        if(maxCount <= uptoHi - uptoLow){
            maxCount = uptoHi - uptoLow;
            sum = s;
        }
    }

    cout << "For sum = " << sum << " number of winner: " << maxCount << endl;

    return 0;
}