每日一练

1.编写一个函数fun，它的功能是：根据以下公式求P的值，p=m!/n!(m-n)! , 结果由函数值带回。m与n为两个正整数，且要求m>n。      

#include<iostream>

using namespacestd;

intfun(unsigned int n,unsigned int m);

intmain()

{

       unsigned int a,b;

      cin>>a>>b;

       if(a>b)

       {

              cout<<"错误，请重新输入：";

              cin>>a>>b;

       }

 

       cout<<fun(a,b)<<'\n';

       return 0;

}

int fun(unsigned int n,unsigned int m)

{

       int num(int x);

       int p,c;

              c=m-n;

              p=num(m)/(num(n)*num(c));

       return p;

}

int num(int x)

{

       int s,i;

       s=1;

       for(i=1;i<=x;i++)

              s=s*i;

       return s;

}