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The fac namespace in C contains the factorial function, which is used to calculate the factorial value of a non-negative integer. Its calculation method is recursive: fac(n) = n * fac(n-1), and returns 1 when n is 0. You can use the fac function directly in your code by including the "using namespace std;" directive.
fac in C
#fac in C is a namespace used to represent the factorial function. The factorial function computes the factorial value of a given nonnegative integer.
Factorial calculation
Factorial calculation uses recursion to calculate the factorial of a given non-negative integer n:
<code class="cpp">int fac(int n) { if (n == 0) { return 1; } else { return n * fac(n - 1); } }</code>
Namespace usage
In order to use the fac namespace, you need to include the following instructions in the code:
<code class="cpp">using namespace std;</code>
After including this instruction, you can use the functions in the fac namespace directly in the code:
<code class="cpp">int result = fac(5); // 计算 5 的阶乘并存储在 result 中</code>
Example
The following code example shows how to calculate the factorial of 5 using the fac namespace:
<code class="cpp">#include <iostream> using namespace std; int main() { int n = 5; int result = fac(n); cout << "5 的阶乘为:" << result << endl; return 0; }</code>
Output result:
<code>5 的阶乘为:120</code>
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