寻找因子和结束0的高价值。 [英] Finding Factorials and Ending 0's for High Values.
问题描述
朋友您好，
我遇到了问题。我想找到大数字的阶乘。
Ex：1555！ =？。
195！ =？。
我的主要问题是我想知道阶乘数的结尾0'的确切数字。
我使用以下公式：
（m！）^ n = m！ = 2 * 10 ^（n-1）+ 2 ^ 2 * 10 ^（n-2）+ ------- + 2 ^ n。
用这个我可以解决其他因子，结束0'的数量就像这样。
100！= 2 * 10 ^ 1 + 2 ^ 2 * 10 ^ 0 = 20 + 4 = 24
100！按此计算有24个结尾0'。
但是，我还有其他问题，
Ex：95！
i）95！ =（100 - 5）！ = 24-2 * 5 ^（1-1）= 24-2 = 22 => 95！已经22 0'了。
ii）95！ =（90 + 5）！ = 9 *（2 * 10 ^ 0）+ 2 * 5 ^ 0）= 18 + 2 = 20 => 95！有20 0'。
这是我的问题。通过使用上面的公式，我得到了两个不同的答案，我很困惑，我没有得到完美的答案所以请帮我找到它。
谢谢...
Hello friends,
I have a problem. I want to find factorial of big numbers.
Ex: 1555! = ?.
195! = ?.
My main problem is that I want to know the exact number of ending 0''s of the factorial numbers.
I use the following formula:
(m!)^n = m! = 2*10^(n-1) + 2^2 * 10^(n-2) + ------- + 2^n.
with this I can solve the other factorials for number of ending 0''s like this.
100!= 2*10^1 + 2^2*10^0 = 20+4 = 24
100! has 24 ending 0''s as per this calculation.
But, then I got other problem,
Ex: For 95!
i) 95! = (100 - 5)! = 24 - 2*5^(1-1) = 24 - 2 = 22 => 95! has 22 0''s.
ii) 95! = (90 + 5)! = 9*(2*10^0) + 2*5^0)= 18+2 = 20 => 95! has 20 0''s.
this is my problem. By using the above formula I got two different answers and I am confused, I don''t get the perfect answer so please help me to find it.
Thank you...
推荐答案
在C中，这并不容易。而且我不知道可用的图书馆;也许别人会为你指出一个。你可以在这里找到一些想法： http：// stackoverflow .com / questions / 3340511 / what-is-the-the-simple-of-implementation-bigint-in-c [ ^ ]。
-SA
In C, this is not so easy. And I don''t know good available library; maybe someone else will point out one for you. You can find some ideas here: http://stackoverflow.com/questions/3340511/what-is-the-simplest-way-of-implementing-bigint-in-c[^].
—SA
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