可能重复:
Calculating large factorials in C++
Howto compute the factorial of x
如何在C ++中实现阶乘函数?我的意思是使用任何参数检查正确实现它,并且错误处理逻辑适用于C ++中的通用数学库。
答案 0 :(得分:35)
递归:
unsigned int factorial(unsigned int n)
{
if (n == 0)
return 1;
return n * factorial(n - 1);
}
迭代:
unsigned int iter_factorial(unsigned int n)
{
unsigned int ret = 1;
for(unsigned int i = 1; i <= n; ++i)
ret *= i;
return ret;
}
编译时间:
template <int N>
struct Factorial
{
enum { value = N * Factorial<N - 1>::value };
};
template <>
struct Factorial<0>
{
enum { value = 1 };
};
void foo()
{
int x = Factorial<4>::value; // == 24
int y = Factorial<0>::value; // == 1
}
答案 1 :(得分:24)
除了明显的循环和递归之外,现代C ++编译器支持将gamma函数作为tgamma()
,与factorial密切相关:
#include <iostream>
#include <cmath>
int main()
{
int n;
std::cin >> n;
std::cout << std::tgamma(n+1) << '\n';
}
答案 2 :(得分:0)
如果安装了Boost,您可能需要查看boost/math/special_functions/factorials.hpp
。您可以在以下网址阅读:Boost Factorial