在python中是否有数学nCr函数？(Is there a math nCr function in python? [duplicate])

 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* or char[N]. Use std::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:
 
 
 
Documentation of std::string
 
 
Hope that helps.