Submission #486419

#	Time	Username	Problem	Language	Result	Execution time	Memory
486419		rainboy	Relay (COI16_relay)	C11	18 / 100	2078 ms	3076 KiB

relay

#include <stdio.h>

#define N	100000
#define M	100000

int xx[N + M], n, m;

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 visible(int i1, int i2, int *xx, int *yy) {
	int j;

	for (j = 0; j < m; j++) {
		int p = (j - 1 + m) % m, q = (j + 1) % m;
		long long c1pj = cross(xx[i1], yy[i1], xx[n + p], yy[n + p], xx[n + j], yy[n + j]);
		long long c1qj = cross(xx[i1], yy[i1], xx[n + q], yy[n + q], xx[n + j], yy[n + j]);
		long long c2pj = cross(xx[i2], yy[i2], xx[n + p], yy[n + p], xx[n + j], yy[n + j]);
		long long c2qj = cross(xx[i2], yy[i2], xx[n + q], yy[n + q], xx[n + j], yy[n + j]);
		long long c1j2 = cross(xx[i1], yy[i1], xx[n + j], yy[n + j], xx[i2], yy[i2]);

		if (c1j2 >= 0 && c1qj >= 0 && c2pj <= 0)
			return 1;
		if (c1j2 <= 0 && c1pj <= 0 && c2qj >= 0)
			return 1;
	}
	return 0;
}

int main() {
	static char good[N];
	static int xx[N], yy[N];
	int i, i1, i2, j, 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 = 1; i1 < n; i1++)
		if (visible(0, i1, xx, yy)) {
			good[i1] = 1;
			for (i2 = 1; i2 < n; i2++)
				if (visible(i1, i2, xx, yy))
					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:40:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   40 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
relay.c:42:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   42 |   scanf("%d%d", &xx[i], &yy[i]);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
relay.c:43:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   43 |  scanf("%d", &m);
      |  ^~~~~~~~~~~~~~~
relay.c:45:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   45 |   scanf("%d%d", &xx[n + j], &yy[n + j]);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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