向上和向下舍入一个数字 C++
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Rounding up and down a number C++
提问by Teo Chuen Wei Bryan
I'm trying to allow my program to round a number up and down respectively.
我试图让我的程序分别向上和向下舍入一个数字。
For example, if the number is 3.6, my program is suppose to round up the nearest number which is 4 and if the number is 3.4, it will be rounded down to 3.
例如，如果数字是3.6，我的程序假设四舍五入最近的数字 4，如果数字是3.4，它将向下四舍五入为 3。
I tried using the ceillibrary to get the average of 3 items.
我尝试使用ceil库来获得 3 个项目的平均值。
results = ceil((marks1 + marks2 + marks3)/3)
results = ceil((marks1 + marks2 + marks3)/3)
However, the ceilonly rounds the number down but does not roll the number up.
但是，ceilonly 会将数字向下舍入但不会向上滚动。
There's 1 algorithm i stumbled upon
我偶然发现了 1 个算法
var roundedVal = Math.round(origVal*20)/20;
var roundedVal = Math.round(origVal*20)/20;
but i still can't figure a formula for some problem.
但我仍然无法找出解决某些问题的公式。
回答by brettmichaelgreen
std::ceil
rounds up to the nearest integer
向上舍入到最接近的整数
std::floor
rounds down to the nearest integer
向下舍入到最接近的整数
std::round
performs the behavior you expect
执行您期望的行为
please give a use case with numbers if this does not provide you with what you need!
如果这不能为您提供您需要的东西，请给出一个带有数字的用例！
回答by Violet Giraffe
回答by MarcD
You don't need a function to round in C or C++. You can just use a simple trick. Add 0.5 and then cast to an integer. That's probably all round does anyway.
您不需要在 C 或 C++ 中舍入的函数。你可以使用一个简单的技巧。添加 0.5，然后转换为整数。无论如何，这可能是全方位的。
double d = 3.1415;
double d2 = 4.7;
int i1 = (int)(d + 0.5);
int i2 = (int)(d2 + 0.5);
i1 is 3, and i2 is 5. You can verify it yourself.
i1是3，i2是5，你可以自己验证。
回答by u3885739
std::roundmay be the one you're looking for. However, bear in mind that it returns a float. You may want to try lroundor llroundto get a result in long or long long (C++ 11).
std::round可能就是你要找的人。但是，请记住它返回一个浮点数。您可能想要尝试lround或llround获得 long 或 long long (C++ 11) 的结果。
回答by Nishita Goyal
In c++, by including cmath library we can use use various functions which rounds off the value both up or down.
在 c++ 中，通过包含 cmath 库，我们可以使用各种函数来向上或向下舍入值。
std::trunc
This simply truncates the decimal part, thas is, the digits after the decimal point no matter what the decimal is.
这只是截断了小数部分，即小数点后的数字，无论小数是什么。
std::ceil
This is used to round up to the closest integer value.
这用于四舍五入到最接近的整数值。
std::floor
This is used to round down to the closest integer value.
这用于向下舍入到最接近的整数值。
std::round
This will round to the nearest integer value whichever is the closest, that is, it can be round up or round down.
这将四舍五入到最接近的整数值，即可以向上或向下四舍五入。
