Submission #508835

#	Time	Username	Problem	Language	Result	Execution time	Memory
508835		rainboy	별자리 (JOI12_constellation)	C11	100 / 100	53 ms	4008 KiB

constellation

/* https://ioi.te.lv/locations/ioi06/contest/day2/points/points_sol.pdf */
#include <stdio.h>

#define N	100000
#define MD	1000000007

unsigned int X = 12345;

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

int xx[N], yy[N], cc[N], o;

long long cross(int i, int j, int k) {
	return (long long) (xx[j] - xx[i]) * (yy[k] - yy[i]) - (long long) (xx[k] - xx[i]) * (yy[j] - yy[i]);
}

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) {
			long long c = cross(o, ii[j], i_);

			if (c == 0)
				j++;
			else if (c < 0) {
				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 solve(int *ii, int n, int c) {
	int i, j, l, l_, r, r_;
	long long ans;

	l_ = 0;
	while (l_ < n && cc[ii[l_]] != c)
		l_++;
	r_ = n - 1;
	while (r_ >= 0 && cc[ii[r_]] != c)
		r_--;
	if (l_ == 0)
		return 0;
	if (l_ == n) {
		ans = 1;
		for (i = 0, j = 1; j <= n; j++)
			if (j == n || cc[ii[j]] == (c ^ 1)) {
				ans += (long long) (j - i) * (j - i - 1) / 2;
				i = j;
			}
		return ans;
	} else {
		for (i = l_; i <= r_; i++)
			if (cc[ii[i]] == (c ^ 1))
				return 0;
		l = l_;
		while (l > 0 && cc[ii[l]] != (c ^ 1))
			l--;
		r = r_;
		while (r < n && cc[ii[r]] != (c ^ 1))
			r++;
		return (long long) (l_ - l) * (r - r_);
	}
}

int main() {
	static int ii[N];
	static char hull[N];
	int n, cnt, h, i, ans;

	scanf("%d", &n);
	o = -1;
	for (i = 0; i < n; i++) {
		scanf("%d%d%d", &xx[i], &yy[i], &cc[i]), cc[i]--;
		if (o == -1 || xx[o] > xx[i] || xx[o] == xx[i] && yy[o] > yy[i])
			o = i;
		ii[i] = i;
	}
	ii[0] = o, ii[o] = 0;
	sort(ii, 1, n);
	cnt = 0;
	for (i = 0; i < n; i++) {
		while (cnt >= 2 && cross(ii[cnt - 2], ii[cnt - 1], ii[i]) >= 0)
			cnt--;
		ii[cnt++] = ii[i];
	}
	for (h = 0; h < cnt; h++)
		hull[ii[h]] = 1;
	ans = (solve(ii, cnt, 0) + solve(ii, cnt, 1)) % MD;
	for (i = 0; i < n; i++)
		if (!hull[i] && cc[i] == -1)
			ans = ans * 2 % MD;
	ans = (ans - 2 + MD) % MD;
	for (i = 0; i < n; i++)
		if (cc[i] == 1) {
			ans = (ans + 1) % MD;
			break;
		}
	for (i = 0; i < n; i++)
		if (cc[i] == 0) {
			ans = (ans + 1) % MD;
			break;
		}
	printf("%d\n", ans);
	return 0;
}

Compilation message (stderr)

constellation.c: In function 'main':
constellation.c:84:50: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   84 |   if (o == -1 || xx[o] > xx[i] || xx[o] == xx[i] && yy[o] > yy[i])
      |                                   ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~
constellation.c:80:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   80 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
constellation.c:83:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   83 |   scanf("%d%d%d", &xx[i], &yy[i], &cc[i]), cc[i]--;
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 10 / 10
• Subtask 10: 10 / 10