Submission #490928

#	Time	Username	Problem	Language	Result	Execution time	Memory
490928		rainboy	Ljetopica (COI19_ljetopica)	C11	17 / 100	1 ms	204 KiB

ljetopica

#include <stdio.h>

#define N	1000
#define MD	1000000007

int pp2[N + 1], vv[N + 1], ff[N + 1], gg[N + 1];

void init() {
	int i;

	pp2[0] = 1;
	for (i = 1; i <= N; i++)
		pp2[i] = pp2[i - 1] * 2 % MD;
	ff[0] = gg[0] = 1;
	for (i = 1; i <= N; i++) {
		vv[i] = i == 1 ? 1 : (long long) vv[i - MD % i] * (MD / i + 1) % MD;
		ff[i] = (long long) ff[i - 1] * i % MD;
		gg[i] = (long long) gg[i - 1] * vv[i] % MD;
	}
}

int choose(int n, int k) {
	return (long long) ff[n] * gg[k] % MD * gg[n - k] % MD;
}

int main() {
	static char cc[N + 1], aa[N + 1], bb[N + 1];
	int n, k;

	init();
	scanf("%d%d%s%s%s", &n, &k, cc, aa, bb);
	printf("%lld\n", (long long) (pp2[n - 1] + pp2[n] - 1) % MD * choose(n - 1, k) % MD);
	return 0;
}

Compilation message (stderr)

ljetopica.c: In function 'main':
ljetopica.c:31:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   31 |  scanf("%d%d%s%s%s", &n, &k, cc, aa, bb);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 8
• Subtask 2: 0 / 14
• Subtask 3: 17 / 17
• Subtask 4: 0 / 61