Dividing prices by 3 | 易学教程

问题

For accounting program I need to divide a price by 3 so it can be shared over 3 months

For example 9€

3€ first month
3€ second month
3€ third month

Now this would be price/3

But what if the number is 10?

3,33€ first month
3,33€ second month
3,33€ last month

3,33€*3 =€9.99

One cent has gone missing. How can I make it so the ouput would become 3,33€ , 3,33€ , 3,34€?

回答1:

As Bathsheba said, ask your users first.

Here's a technique that I've used often in such scenarios. This method will ensure the most even distribution, with the upward bias toward the end. For example, if you call DivvyUp(101, 3), you'll get 33.66, 33.67, 33.67. Notice that the difference isn't just made up for at the end. Instead, each value is computed according to what's left, not what was started with.

public static double[] DivvyUp(double total, uint count)
{
    var parts = new double[count];
    for (var i = 0; i < count; ++i)
    {
        var part = Math.Truncate((100d * total) / (count - i)) / 100d;
        parts[i] = part;
        total -= part;
    }
    return parts;
}

回答2:

You need to ask the accountant what they would want here. That's an important thing to do in software development: ask the users.

Normally, for stability, you would subtract the amounts paid from a balance account, and put checks in to ensure that the balance falls to zero.

And don't ever use a floating point data type when building accounting software. Floating point precision will bite you. Use a currency type instead.

回答3:

You could set the last by making up the difference, instead of via the same calculation as the rest. In pseudocode:

normalMonthPrice = RoundToTwoPlaces(totalPrice / months);
lastMonthPrice = totalPrice - (normalMonthPrice * (months - 1));

回答4:

Congratulations, you've found out why the computing world isn't as simple as "put math on it"-

The easiest solution would be to divide by 3, round to two decimal places, and use that value for the first two months, and original - 2 * perMonth for the rest.

来源：https://stackoverflow.com/questions/21914074/dividing-prices-by-3

标签

math

numbers