Submission #378435

#	Time	Username	Problem	Language	Result	Execution time	Memory
378435		rainboy	Boat (APIO16_boat)	C11	9 / 100	511 ms	512 KiB

boat

#include <stdio.h>

#define N	500
#define MD	1000000007

unsigned int X = 12345;

int rand_() {
	return (X *= 3) >> 1;
}

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

void init() {
	int i;

	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 xx[N * 2];

void sort(int *ii, int l, int r) {
	while (l < r) {
		int i = l, j = l, k = r, i_ = ii[l + rand_() % (r - l)], tmp;

		while (j < k)
			if (xx[ii[j]] == xx[i_])
				j++;
			else if (xx[ii[j]] < xx[i_]) {
				tmp = ii[i], ii[i] = ii[j], ii[j] = tmp;
				i++, j++;
			} else {
				k--;
				tmp = ii[j], ii[j] = ii[k], ii[k] = tmp;
			}
		sort(ii, l, i);
		l = k;
	}
}

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

int main() {
	static int ii[N * 2], xx_[N * 2], dp[N + 1];
	int n, h, i, j, ans;

	init();
	scanf("%d", &n);
	for (i = 0; i < n; i++) {
		scanf("%d%d", &xx[i << 1 | 0], &xx[i << 1 | 1]);
		xx[i << 1 | 1]++;
	}
	for (i = 0; i < n * 2; i++)
		ii[i] = i;
	sort(ii, 0, n * 2);
	for (i = 0; i < n * 2; i++)
		xx_[i] = xx[ii[i]], xx[ii[i]] = i;
	dp[0] = 1;
	for (h = 0; h + 1 < n * 2; h++) {
		int x = xx_[h + 1] - xx_[h];

		if (x > 0)
		for (j = n; j > 0; j--)
			if (xx[j - 1 << 1 | 0] <= h && h < xx[j - 1 << 1 | 1]) {
				int k;

				k = 0;
				for (i = j - 1; i >= 0; i--)  {
					if (xx[i << 1 | 0] <= h && h < xx[i << 1 | 1])
						k++;
					dp[j] = (dp[j] + dp[i] * choose(k + x - 1, x - 1)) % MD;
				}
			}
	}
	ans = 0;
	for (i = 1; i <= n; i++)
		ans = (ans + dp[i]) % MD;
	printf("%d\n", ans);
	return 0;
}

Compilation message (stderr)

boat.c: In function 'main':
boat.c:71:13: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
   71 |    if (xx[j - 1 << 1 | 0] <= h && h < xx[j - 1 << 1 | 1]) {
      |           ~~^~~
boat.c:71:44: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
   71 |    if (xx[j - 1 << 1 | 0] <= h && h < xx[j - 1 << 1 | 1]) {
      |                                          ~~^~~
boat.c:55:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   55 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
boat.c:57:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   57 |   scanf("%d%d", &xx[i << 1 | 0], &xx[i << 1 | 1]);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 0 / 22
• Subtask 3: 0 / 27
• Subtask 4: 0 / 42