1100: finding the number of combinations (function topic)

Title Description

There will be a new programming competition soon , What's different is that , This competition is based on class , In order to comprehensively measure the overall level of a class , Ask from a class m Choose from students k Students represent our class in the competition , Ask how many combinations there are . obviously , This combination number is m!/(k!(m-k)!). Ask to write a function fact(), Realize the factorial function of finding a number , This function is called in the main function . 
long fact(long n)

{ 
   // The return value of the function is n The factorial . 
} 

Input

Enter two positive integers m,k,k<=m<=12.

Output

Output an integer , That is, the number of combination schemes .

The sample input  Copy

5 3

Sample output  Copy

10

The code and detailed analysis are shown below ：

#include <stdio.h>
#include <stdlib.h>
long fact(long n);
int main()
{
    long m,k;
    scanf("%ld %ld",&m,&k);
    long mm,kk,pp; //mm by m The factorial ,kk by k The factorial ,pp by （m-k） The factorial 
    mm= fact(m);
    kk= fact(k);
    pp= fact(m-k);
    long fa=mm/(kk*(pp));
    printf ("%ld",fa);
    return 0;
}
long fact(long n)
{

    long s=1;  //s The factorial value used to store the passed in value 
    for (;n>0;n--)
    {
        s=s*n;
    }

    return s;

    // The return value of the function is n The factorial 
}