Submission #486440

#	Time	Username	Problem	Language	Result	Execution time	Memory
486440		rainboy	Relay (COI16_relay)	C11	37 / 100	2060 ms	2792 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 compare(int x1, int y1, int x2, int y2) {
	int sgn1 = x1 < 0 || x1 == 0 && y1 < 0 ? -1 : 1;
	int sgn2 = x2 < 0 || x2 == 0 && y2 < 0 ? -1 : 1;
	long long c;

	if (sgn1 != sgn2)
		return sgn1 - sgn2;
	c = cross2(x1, y1, x2, y2);
	return c == 0 ? 0 : (c > 0 ? -1 : 1);
}

int visible(int i1, int i2) {
	int xl1 = xxl[i1], yl1 = yyl[i1], xr1 = xxr[i1], yr1 = yyr[i1];
	int xl2 = xxl[i2], yl2 = yyl[i2], xr2 = xxr[i2], yr2 = yyr[i2];
	int l1r1 = compare(xl1, yl1, xr1, yr1) <= 0;
	int r1l2 = compare(xr1, yr1, xl2, yl2) < 0;
	int l2r2 = compare(xl2, yl2, xr2, yr2) <= 0;
	int r2l1 = compare(xr2, yr2, xl1, yl1) < 0;

	return !(l1r1 && r1l2 && l2r2 || r1l2 && l2r2 && r2l1 || l2r2 && r2l1 && l1r1 || r2l1 && l1r1 && r1l2);
}

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 (i = 0; i < n; i++)
		for (j = 0; j < m; j++) {
			p = (j - 1 + m) % m, q = (j + 1) % m;
			if (cross(xx[i], yy[i], xx[n + p], yy[n + p], xx[n + j], yy[n + j]) >= 0
					&& cross(xx[i], yy[i], xx[n + q], yy[n + q], xx[n + j], yy[n + j]) > 0)
				xxl[i] = xx[i] - xx[n + j], yyl[i] = yy[i] - yy[n + j];
			if (cross(xx[i], yy[i], xx[n + q], yy[n + q], xx[n + j], yy[n + j]) <= 0
					&& cross(xx[i], yy[i], xx[n + p], yy[n + p], xx[n + j], yy[n + j]) < 0)
				xxr[i] = xx[n + j] - xx[i], yyr[i] = yy[n + j] - yy[i];
		}
	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 'compare':
relay.c:17:31: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   17 |  int sgn1 = x1 < 0 || x1 == 0 && y1 < 0 ? -1 : 1;
      |                       ~~~~~~~~^~~~~~~~~
relay.c:18:31: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   18 |  int sgn2 = x2 < 0 || x2 == 0 && y2 < 0 ? -1 : 1;
      |                       ~~~~~~~~^~~~~~~~~
relay.c: In function 'visible':
relay.c:35:24: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   35 |  return !(l1r1 && r1l2 && l2r2 || r1l2 && l2r2 && r2l1 || l2r2 && r2l1 && l1r1 || r2l1 && l1r1 && r1l2);
      |           ~~~~~~~~~~~~~^~~~~~~
relay.c:35:72: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   35 |  return !(l1r1 && r1l2 && l2r2 || r1l2 && l2r2 && r2l1 || l2r2 && r2l1 && l1r1 || r2l1 && l1r1 && r1l2);
      |                                                           ~~~~~~~~~~~~~^~~~~~~
relay.c:35:96: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   35 |  return !(l1r1 && r1l2 && l2r2 || r1l2 && l2r2 && r2l1 || l2r2 && r2l1 && l1r1 || r2l1 && l1r1 && r1l2);
      |                                                                                   ~~~~~~~~~~~~~^~~~~~~
relay.c: In function 'main':
relay.c:42:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   42 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
relay.c:44:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   44 |   scanf("%d%d", &xx[i], &yy[i]);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
relay.c:45:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   45 |  scanf("%d", &m);
      |  ^~~~~~~~~~~~~~~
relay.c:47:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   47 |   scanf("%d%d", &xx[n + j], &yy[n + j]);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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