C#：如何对整数进行四舍五入的简单数学运算？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/299094/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
C#: How do I do simple math, with rounding, on integers?
提问by Ian Boyd
i want the result of an equation rounded to the nearest integer. e.g.
我想要一个方程的结果四舍五入到最接近的整数。例如
137 * (3/4) = 103
Consider the following incorrect code.
考虑以下不正确的代码。
int width1 = 4;
int height1 = 3;
int width2 = 137;
int height2 = width2 * (height1 / width1);
What is the proper way to perform "integer" math in C#?
在 C# 中执行“整数”数学的正确方法是什么？
Do i really have to do:
我真的必须这样做吗：
int height2 = (int)Math.Round(
(float)width2 * ((float)height1 / (float)width1)
);
采纳答案by Aaron
As said above, you should do the multiplication before the division. Anyway you could write your expression with casting only the divisor:
如上所述，您应该在除法之前进行乘法。无论如何，您可以只使用除数来编写表达式：
int height2 = (int)Math.Round(width2 * (height1 / (float)width1));
回答by Jeffrey L Whitledge
int height2 = (width2 * height1) / width1;
回答by James Curran
The elaborate on Jeffery's message, since you generally a better chance of truncated needed decimals than you have of overflowing a 32-bit integer (and because multiplication & division is commutative), you should generally do multiplication before division.
Jeffery 消息的详细说明，因为与溢出 32 位整数相比，通常截断所需小数的机会更好（并且因为乘法和除法是可交换的），所以您通常应该在除法之前进行乘法。
回答by plinth
Do multiplication first (as long as they're not likely to overflow) and division second.
首先进行乘法（只要它们不太可能溢出）然后进行除法。
3/4 == 0 in integer math (integer math doesn't round on division, it truncates).
整数数学中的 3/4 == 0（整数数学不舍入除法，而是截断）。
If you really need rounding, you have to either work in fixed point, floating point, or play around with the modulus.
如果您确实需要舍入，则必须以定点、浮点或模数进行操作。
回答by dongilmore
int height2 = ((width2 * height1 * 10) + 5) / (width1 * 10);
Prior to any integer division, check to make certain the divisor is not zero. Also note this assumes positive quotient. If negative, roundoff needs to be -5, not +5.
在进行任何整数除法之前，请检查以确保除数不为零。另请注意，这假定为正商。如果为负，则舍入需要为 -5，而不是 +5。
回答by andrewrk
I will fix the incorrect code by adding zero lines of code:
我将通过添加零行代码来修复不正确的代码：
float width1 = 4;
float height1 = 3;
float width2 = 137;
float height2 = width2 * (height1 / width1);
You should use floats for variables that can possibly contain decimals. This includes heights calculated from ratios. You can always cast to int later if that is a problem.
对于可能包含小数的变量，您应该使用浮点数。这包括根据比率计算的高度。如果这是一个问题，您可以稍后再转换为 int。
回答by rwallace
Never cast to float, it has even less precision than a 32-bit integer. If you're going to use floating point, always use double instead of float.
永远不要转换为浮点数，它的精度甚至低于 32 位整数。如果要使用浮点数，请始终使用 double 而不是 float。
回答by Ruben
I think this is the most elegant way to do this:
我认为这是最优雅的方法：
Math.round(myinteger * 0.75);
Using 0.75 instead of 3/4 will implicitly cast it to an double/float and why not use the default functions that are provided for this?
使用 0.75 而不是 3/4 会将其隐式转换为双精度/浮点数，为什么不使用为此提供的默认函数？
回答by Tod
Convert's conversions always round so:
Convert 的转换总是四舍五入：
int height2 = Convert.ToInt32(width2 * height1 / (double)width1);
回答by Pianoman
Just stumbled upon this question. Aaron's answer seems almost right to me. But I'm very sure you need to specify midpointrounding if your problem is a "real world" problem. So my answer, based on Aaron's code, is
刚刚偶然发现了这个问题。亚伦的回答对我来说几乎是正确的。但是我很确定如果您的问题是“现实世界”问题，您需要指定中点舍入。所以我的答案，基于 Aaron 的代码，是
int height2 = (int)Math.Round(width2 * (height1 / (float)width1),MidpointRounding.AwayFromZero);
To see the difference run that code in console
要查看差异，请在控制台中运行该代码
Console.WriteLine((int)Math.Round(0.5));
Console.WriteLine((int)Math.Round(1.5));
Console.WriteLine((int)Math.Round(2.5));
Console.WriteLine((int)Math.Round(3.5));
Console.WriteLine((int)Math.Round(0.5, MidpointRounding.AwayFromZero));
Console.WriteLine((int)Math.Round(1.5, MidpointRounding.AwayFromZero));
Console.WriteLine((int)Math.Round(2.5, MidpointRounding.AwayFromZero));
Console.WriteLine((int)Math.Round(3.5, MidpointRounding.AwayFromZero));
Console.ReadLine();
For details you may look at thisarticle.
有关详细信息，您可以查看这篇文章。
