Round to 25, 50, 75, 100

问题

I'm not a Math person so I'm having a hard time to come up with a calculation to round the decimals to 25, 50, 75 and 100. And this will not be the typical round off because the decimals will not be decreased but only increased.

Example:

if 11.12, round to 11.25

if 11.34, round to 11.50

if 11.52, round to 11.75

if 11.76, round to 12.00

Here's my starting method:

public float RoundNearestCents(String price)
    {
        float srp;

        return srp;
    }

回答1:

public float RoundNearestCents(double d)
{
  return (double)(Math.Ceiling(d * 4)) / 4;
}

回答2:

I suggest using types without floating point.

decimal RoundNearestCents(decimal price) {
    // no problems with floating point as all calculations are exact
    return Math.Floor((price * 100 + 24) / 25) * 25 / 100;
}

-- Why is your price string?

-- Because it's coming from a textbox.

I assume your textbox should support limiting your input to decimal numbers with at most 2 decimal places. So its value will be decimal already. However I don't know what is your application type. If you still want to accept string then consider using decimal.TryParse method to convert it to decimal.

回答3:

My code may not be the best out there, but it will work. In your function create a float and an int like so.

public float RoundNearestCents(String price)
{
    float srp = float.Parse(price);
    int srp1 = Int32.Parse(price);
    if((srp-srp1)>=0.5) 
        srp1++;
    else 
        return srp1;
    return srp1;
}

The int would truncate out the decimal part, which is like flooring the price.

回答4:

I would use something like this:

float RoundNearestCents(float price)
    {
    price*=(100/25.0); // now fractions are going away
    if (price-floor(price)>=0.5) price++; // round up if fraction above 0.5
    return floor(price)*(25.0/100.0); // cut of the fraction and restore original range
    }

回答5:

This is one way:

public decimal RoundNearestCents(decimal price)
{
    decimal srp = price * 100;
    decimal m = srp % 25;
    srp = srp - m + (m > 0 ? 25 : 0);
    return srp / 100;
}

来源：https://stackoverflow.com/questions/35955024/round-to-25-50-75-100

标签

math

rounding