UVA 11481 - Arrange the Numbers（组合数学）

#include <stdio.h>
#include <string.h>

const long long MOD = 1000000007;

const int N = 1005;

int t, n, m, k;
long long dp[N], C[N][N];

void init() {
	dp[0] = 1; dp[1] = 0; dp[2] = 1;
	for (int i = 3; i <= 1000; i++)
		dp[i] = (i - 1) * ((dp[i - 2] + dp[i - 1]) % MOD) % MOD;
	for (int i = 0; i <= 1000; i++) {
		C[i][0] = C[i][i] = 1;
  		for (int j = 1; j < i; j++) {
			C[i][j] = (C[i - 1][j - 1] + C[i - 1][j]) % MOD;
  		}
	}
}

int main() {
	int cas = 0;
	init();
	scanf("%d", &t);
 	while (t--) {
  		scanf("%d%d%d", &n, &m, &k);
  		long long ans = 0;
  		for (int i = 0; i <= n - m; i++)
  			ans = (ans + C[n - m][i] * dp[n - k - i] % MOD) % MOD;
  		printf("Case %d: %lld\n", ++cas, ans * C[m][k] % MOD);
  	}	
	return 0;
}