在python中是否有数学nCr函数?(Is there a math nCr function in python? [duplicate])
可能的重复:
统计:Python中的组合
有效地计数组合和排列
python中的项目欧拉问题(问题53)我正在看看是否内置了python中的数学库是nCr(n Choose r)函数:
我知道这可以编程,但是我以为我会检查它是否已经建立在我之前。
Possible Duplicates:
Statistics: combinations in Python
counting combinations and permutations efficiently
Project euler problem in python (problem 53)I'm looking to see if built in with the math library in python is the nCr (n Choose r) function:
I understand that this can be programmed but I thought that I'd check to see if it's already built in before I do.
原文:https://stackoverflow.com/questions/4941753
满意答案
首先,不要使用
char*
或char[N]
。 使用std::string
,然后一切都变得很容易!例子,
std::string s = "Hello"; std::string greet = s + " World"; //concatenation easy!
容易,不是吗?
现在如果你需要
char const *
的某些原因,比如当你想传递一些功能,那么你可以这样做:some_c_api(s.c_str(), s.size());
假设此函数声明为:
some_c_api(char const *input, size_t length);
从这里开始探索
std::string
自己:
- std :: string的文档
希望有帮助。
First of all, don't use
char*
orchar[N]
. Usestd::string
, then everything else becomes so easy!Examples,
std::string s = "Hello"; std::string greet = s + " World"; //concatenation easy!
Easy, isn't it?
Now if you need
char const *
for some reason, such as when you want to pass to some function, then you can do this:some_c_api(s.c_str(), s.size());
assuming this function is declared as:
some_c_api(char const *input, size_t length);
Explore
std::string
yourself starting from here:Hope that helps.
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