杭电ACM2048题
#include<stdio.h>
int main ()
{
long long s[21], sum;
int i, n, m;
scanf("%d",&n);
while (n--)
{
scanf("%d",&m);
s[0] = 0;
s[1] = 0;
s[2] = 1;
s[3] = 2;
sum = 2;
for (i = 3; i<=m; i++)
{
s[i] = (i-1)*(s[i-1]+s[i-2]);
sum = sum*i;
}
printf("%.2f%%\n",s[m]*100.0/sum);
}
return 0;
}