Rejection of the correct answer

The system rejects my answer for Problem 37, although it is definitely correct, I can prove it.

input data: 3000000 7 96

My program returned the answer 40901, while the system insists on the answer 40902. This code is my apology:

public class MyClass {
    public static void main(String[] args) {
        int m = 0;
        long p = 3000000L;
        System.out.print("| Month | Balance |\n|-------|---------|");
        do {
            ++m;
            p *= 1207L;
            p /= 1200L;
            p -= 40901L;
            System.out.print(String.format("\n| %5d | %7d |", m, p));
        } while (p > 0);
    }
}

By the way, if you are converting from integers to real numbers and vice versa, then you are doing it wrong. You can get the idea from my code. If you want, I can send my program by e-mail or publish it here.

With deepest respect and hope for fruitful cooperation, Kulbas Oglydov.

Of course. Does the condition of the problem say something else?

Thank you, I understand. However, this is not clearly mentioned in the problem statement. In any case, this does not mean that real numbers cannot be dispensed with. I solved the problem without them. A similar situation arose in the "Duel Chances" problem. I still try not to use real numbers in integer calculations unless absolutely necessary.

public class MyClass {
    public static void main(String[] args) {
        final Scanner s = new Scanner(System.in);
        int m = 0;
        long p = 3000000L;
        System.out.print("| Month | Balance |\n|-------|---------|");
        do {
            ++m;
            p *= 1207L;
            p += 600L;
            p /= 1200L;
            p -= 40901L;
            System.out.print(String.format("\n| %5d | %7d |", m, p));
        } while (p > 0);
    }
}

Real numbers in a computer are not as precise as they are in pure mathematics. The computer may have rounding errors. In fact, I strive to solve problems in rational numbers, not integers. I could even make an appropriate class, but for such simple tasks it is usually redundant.

The fact that the probability of an event is between 0 and 1 does not matter in this case. I just express these numbers in a different way. For example, in hundredths, as in that case.

Such practices are not so rare. For example, in computer games, you may not want to calculate trigonometric functions using mathematic library. It is better to store a table of 360 values (or 256, or 65536, it's implementation details, of course). And these values will be integer. For example, one thousandth of a unit (or 1/255, or 1/65535), if such accuracy is sufficient. In other words, sin(0) = 0, sin(30) = 500 instead of 0.5, sin(60) = 866 instead of 0.866, sin(90) = 1000 instead of 1.0, and so on. I heard that similar techniques are used in professional neural networks implementations. However, in this matter I am not competent enough.

It may seem strange to the younger generation, but I started out programming 8-bit processors that couldn't even multiply. Therefore, when I wanted to multiply a number by 5, I doubled it twice, then added the original one. Of course, now I don’t do that, but such a search for the way with minimal effort (for processor, not brain) is already working on a subconscious level.

For example, when I calculate the roots of a quadratic equation, I do not divide them by (a * 2). I calculate (0.5 / a) and then multiply both roots by that number. This is mathematically equivalent, but I am replacing one multiplication and two divisions with one division and two multiplications. Computers multiply much faster and more accurately than they divide.

You can see how I solved the "Whisky Blending" if you're curious. It looks crazy, but works.

I love strange techniques from an era when people could think, and not just include libraries. Recently I saw a headline on YouTube: How to make Tetris on Unity. This was the last straw after which I stopped going to YouTube. Other social networks have never been used by me at all.

By the way, I just had an idea! Why not make a Tetris-themed problem? For example, removing filled lines. Although this is probably too easy, but that's the first thing that came to mind.