ALGO Back-polynom Reversible String Hash

#include <iostream>
#include  <string>
using namespace std;
typedef signed long long ll;
typedef   unsigned  long ui;

const ll MaxN(19091), mul(7), mod(19e6+7); ll deg[MaxN] = {1};
struct subcmp {
    char str[MaxN], rtr[MaxN]; ui size;
    ll suff[MaxN] = {}, pref[MaxN] = {};
    void get_deg() {
        for (ll* i(deg + 1); i < deg + size + 19; ++i)
            *i = (*(i - 1) * mul) % mod;
    }
    subcmp (string& s) {
        size = s.size(); get_deg();
        for (ui i(0); i < size; ++i)
            str[i] = rtr[size-i-1] = s[i];
        for (ui i(0); i < size; ++i)
            pref[i + 1] = (pref[i] * mul + str[i]) % mod,
            suff[i + 1] = (suff[i] * mul + rtr[i]) %mod;
    }
    ll get (ll i, ll j, bool rev) {
        if (rev)    value = suff[size-j] - suff[size-i-1] * deg[i-j+1];
        else        value = pref[j + 1] - pref[i] * deg[j-i+1];
        while (value < 0) value += mod;
        return value;
    }
};