HDU 2049 不容易系列之(4)——考新郎

#include<stdio.h>
long long num[25],N[25];
int main( )
{
    num[1] = 0;
    num[2] = 1;
    N[1] = 1;
    N[2] = 2;
    N[0] = 1;
    for( int i = 3; i < 25; ++i )
         num[i] = ( num[i-1] + num[i-2] )*( i - 1 ),N[i] = i * N[i-1];
    int t,n,m;
    scanf( "%d",&t );
    while( t-- )
    {
           scanf( "%d%d",&n,&m );
           printf( "%I64d\n",N[n] /  N[n-m] / N[m]  *num[m]   );
           }
    return 0;
}