Submission #503222

#	Time	Username	Problem	Language	Result	Execution time	Memory
503222		rainboy	Magneti (COCI21_magneti)	C11	30 / 110	302 ms	460 KiB

Main

#include <stdio.h>

#define N	50
#define M	10000
#define MD	1000000007

int max(int a, int b) { return a > b ? a : b; }

int vv[M + 1], ff[M + 1], gg[M + 1];

void init() {
	int i;

	ff[0] = gg[0] = 1;
	for (i = 1; i <= M; 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 k < 0 || k > n ? 0 : (long long) ff[n] * gg[k] % MD * gg[n - k] % MD;
}

int pp[N], rr[N], n, l, ans; char used[N];

void branch(int i) {
	if (i == n) {
		int d = 0;

		for (i = 1; i < n; i++)
			d += max(rr[pp[i]], rr[pp[i - 1]]) - 1;
		ans = (ans + (long long) choose(l - d, n)) % MD;
		return;
	}
	for (pp[i] = 0; pp[i] < n; pp[i]++)
		if (!used[pp[i]])
			used[pp[i]] = 1, branch(i + 1), used[pp[i]] = 0;
}

int main() {
	int i;

	init();
	scanf("%d%d", &n, &l);
	for (i = 0; i < n; i++)
		scanf("%d", &rr[i]);
	if (n <= 10) {
		branch(0);
		printf("%d\n", ans);
	} else
		printf("%lld\n", (long long) choose(l - (rr[0] - 1) * (n - 1), n) * ff[n] % MD);
	return 0;
}

Compilation message (stderr)

Main.c: In function 'main':
Main.c:46:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   46 |  scanf("%d%d", &n, &l);
      |  ^~~~~~~~~~~~~~~~~~~~~
Main.c:48:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   48 |   scanf("%d", &rr[i]);
      |   ^~~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 20 / 20
• Subtask 3: 0 / 30
• Subtask 4: 0 / 50