Submission #486431

#	Time	Username	Problem	Language	Result	Execution time	Memory
486431		rainboy	Relay (COI16_relay)	C11	0 / 100	2 ms	204 KiB

relay

#include <stdio.h>

#define N	100000
#define M	100000

long long cross2(int x1, int y1, int x2, int y2) {
	return (long long) x1 * y2 - (long long) x2 * y1;
}

long long cross(int x0, int y0, int x1, int y1, int x2, int y2) {
	return cross2(x1 - x0, y1 - y0, x2 - x0, y2 - y0);
}

int xx[N + M], yy[N + M], xxl[N], yyl[N], xxr[N], yyr[N];

int visible(int i1, int i2) {
	return cross2(xxr[i1], yyr[i1], xxl[i2], yyl[i2]) <= 0 || cross2(xxr[i2], yyr[i2], xxl[i1], yyl[i1]) <= 0;
}

int main() {
	static char good[N];
	int n, m, i, i1, i2, j, p, q, k;

	scanf("%d", &n);
	for (i = 0; i < n; i++)
		scanf("%d%d", &xx[i], &yy[i]);
	scanf("%d", &m);
	for (j = 0; j < m; j++)
		scanf("%d%d", &xx[n + j], &yy[n + j]);
	for (i1 = 0; i1 < n; i1++) {
		for (j = 0; j < m; j++) {
			p = (j - 1 + m) % m, q = (j + 1) % m;
			if (cross(xx[i1], yy[i1], xx[n + p], yy[n + p], xx[n + j], yy[n + j]) >= 0 && cross(xx[i1], yy[i1], xx[n + q], yy[n + q], xx[n + j], yy[n + j]) > 0)
				xxl[i1] = xx[i1] - xx[n + j], yyl[i1] = yy[i1] - yy[n + j];
			if (cross(xx[i1], yy[i1], xx[n + q], yy[n + q], xx[n + j], yy[n + j]) <= 0 && cross(xx[i1], yy[i1], xx[n + p], yy[n + p], xx[n + j], yy[n + j]) < 0)
				xxr[i1] = xx[n + j] - xx[i1], yyr[i1] = yy[n + j] - yy[i1];
		}
	}
	for (i1 = 1; i1 < n; i1++)
		if (visible(0, i1)) {
			good[i1] = 1;
			for (i2 = 1; i2 < n; i2++)
				if (visible(i1, i2))
					good[i2] = 1;
		}
	k = 0;
	for (i = 1; i < n; i++)
		if (good[i])
			k++;
	printf("%d\n", k);
	return 0;
}

Compilation message (stderr)

relay.c: In function 'main':
relay.c:24:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   24 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
relay.c:26:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   26 |   scanf("%d%d", &xx[i], &yy[i]);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
relay.c:27:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   27 |  scanf("%d", &m);
      |  ^~~~~~~~~~~~~~~
relay.c:29:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   29 |   scanf("%d%d", &xx[n + j], &yy[n + j]);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 18
• Subtask 2: 0 / 19
• Subtask 3: 0 / 20
• Subtask 4: 0 / 43