10105 - Polynomial Coefficients

描述：杨辉三角与二项式定理

#include <cstdio>

int solve(int n,int m)

{

    int sum=1;

    for(int i=n; i>m; --i) sum*=i;

    for(int i=2; i<=n-m; ++i) sum/=i;

    return sum;

}

int main()

{

    //freopen("a.txt","r",stdin);

    int n,m,sum,k;

    while(scanf("%d%d",&n,&m)!=EOF)

    {

        sum=1;

        for(int i=0; i<m; i++)

        {

            scanf("%d",&k);

            if(k)

            {

                sum*=solve(n,k);

                n-=k;

            }

        }

        printf("%d\n",sum);

    }

    return 0;

}