題目大意:
在
思路:
從
即:
#include <iostream>
#include <cstdio>
#define LL long long
using namespace std;
LL c[50][50];
void init()
{
for (int i = 0; i <= 31; i++)
{
c[i][0] = 1;
}
for (int i = 1; i <= 31; i++)
{
for (int j = 1; j <= i; j++)
{
c[i][j] = c[i - 1][j - 1] + c[i - 1][j];
}
}
}
int main()
{
init();
int T;
scanf("%d", &T);
for (int cas = 1; cas <= T; cas++)
{
LL n, k;
scanf("%lld%lld", &n, &k);
printf("Case %d: ", cas);
if (n < k)
{
printf("0\n");
continue;
}
LL sum;
sum = c[n][k];
while (k--)
{
sum *= n;
n--;
}
printf("%lld\n", sum);
}
return 0;
}