22 lines
413 B
C
22 lines
413 B
C
#include<stdio.h>
|
|
unsigned long long sum[21],f[21];
|
|
int main()
|
|
{
|
|
int i,t,n,m;
|
|
f[0]=0;f[1]=0;f[2]=1;
|
|
sum[0]=1;sum[1]=1;
|
|
for(i=2;i<=20;i++)
|
|
{
|
|
sum[i]=sum[i-1]*i;
|
|
if(i>=3)
|
|
f[i]=(i-1)*(f[i-1]+f[i-2]);
|
|
}
|
|
scanf("%d",&t);
|
|
while(t--)
|
|
{
|
|
scanf("%d%d",&n,&m);
|
|
printf("%llu\n",sum[n]/sum[m]/sum[n-m]*f[m]);
|
|
}
|
|
return 0;
|
|
}
|