hey can you please clear one doubt in F. i saw your code. i think f denotes whether b is bigger than a or not and t checks that b must be less than n. now,

if (t){
        if ((n >> i) & 1){
            ans += rec(i - 1, f, 0); // 00
            ans += rec(i - 1, f, 1); // 11
            if (f) ans += rec(i - 1, 0, 1); // this is what you are doing
            else ans += 2 * rec(i - 1, 0, 1); 
        }else ans += rec(i - 1, f, t);
    }

and this is what my mind says

if (t){
        if ((n >> i) & 1){
            ans += rec(i - 1, f, 0); // 00
            ans += rec(i - 1, f, 1); // 11
            if (f) ans += rec(i - 1, 0, 1); // 01
            else ans += rec(i - 1, 0, 1) + rec(i-1, 0, 0);//this is what my mind says
// because if we put 1 in a and 0 in b then t should be zero because b became less than n.
        }else ans += rec(i - 1, f, t);
    }

Do you understand what i am saying?

I’m under 13 yrs old, so when I am registering discord blocked me:sadge: