计算在C＃阶乘 [英] Calculate factorials in C#
问题描述
您如何计算使用C＃大阶乘？ Windows中的计算器在Win 7溢出的阶乘（3500）。作为一种编程和数学问题，我想知道你怎么能计算出更多数量的阶乘（20000，可能是）在C＃。任何指针？
How can you calculate large factorials using C#? Windows calculator in Win 7 overflows at Factorial (3500). As a programming and mathematical question I am interested in knowing how you can calculate factorial of a larger number (20000, may be) in C#. Any pointers?
我刚检查了在Win 2K3一个计算的，因为我记得做在Win 2K3一个更大的阶乘。我很惊讶的事情摸索出了道路。
I just checked with a calc on Win 2k3, since I could recall doing a bigger factorial on Win 2k3. I was surprised by the way things worked out.
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计算器上WIN2K3合作过，甚至大的数字。我试过！50000，我得到了一个答案，3.3473205095971448369154760940715e + 213236
Calc on Win2k3 worked with even big numbers. I tried !50000 and I got an answer, 3.3473205095971448369154760940715e+213236
这是非常快的，而我做了这一切。
It was very fast while I did all this.
这里的主要问题是不仅要找出适当的数据类型，但也有点数学。如果我尝试写一个简单的阶乘code在C＃[递归或循环]，表现实在是太差了。它需要多秒得到答案。如何在Windows 2K3（或XP）的钙能在不到10秒内未执行这样一个庞大的阶乘？有没有在C＃中计算阶乘编程的任何其他方式？
The main question here is not only to find out the appropriate data type, but also a bit mathematical. If I try to write a simple factorial code in C# [recursive or loop], the performance is really bad. It takes multiple seconds to get an answer. How is the calc in Windows 2k3 (or XP) able to perform such a huge factorial in less than 10 seconds? Is there any other way of calculating factorial programmatically in C#?
推荐答案
有一个看的BigInteger 结构：
Have a look at the BigInteger structure:
<一个href="http://msdn.microsoft.com/en-us/library/system.numerics.biginteger.aspx">http://msdn.microsoft.com/en-us/library/system.numerics.biginteger.aspx
也许这可以帮助你实现这个功能。
Maybe this can help you implement this functionality.
$ C $的CProject具有<一个旧版本的框架的实现href="http://www.$c$cproject.com/KB/cs/biginteger.aspx">http://www.$c$cproject.com/KB/cs/biginteger.aspx.
CodeProject has an implementation for older versions of the framework at http://www.codeproject.com/KB/cs/biginteger.aspx.
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