Submission #208282

#	Time	Username	Problem	Language	Result	Execution time	Memory
208282		dolphingarlic	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	28 ms	31608 KiB

kangaroo

#include <cstdio>
using namespace std;

const long long MOD = 1e9 + 7;

long long dp[2001][2001];

int main() {
	int n, a, b;
	scanf("%d %d %d", &n, &a, &b);
	dp[0][0] = 1;
	for (int i = 1; i <= n; i++) for (int j = 1; j <= n; j++) {
		if (i == a || i == b)
			dp[i][j] = (dp[i - 1][j] + dp[i - 1][j - 1]) % MOD;
		else
			dp[i][j] = (dp[i - 1][j + 1] * j + dp[i - 1][j - 1] * (j - (i > a) - (i > b))) % MOD;
	}
	printf("%lld\n", dp[n][1]);
	return 0;
}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:10:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d %d", &n, &a, &b);
  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 6 / 6
• Subtask 2: 30 / 30
• Subtask 3: 15 / 15
• Subtask 4: 49 / 49