Submission #548850

# Submission time Handle Problem Language Result Execution time Memory
548850 2022-04-14T15:09:47 Z rainboy Printed Circuit Board (CEOI12_circuit) C
85 / 100
31 ms 1096 KB
#include <assert.h>
#include <stdio.h>

#define N	200000

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

int xx[N], yy[N], n;

long long cross2(int i, int j) {
	i %= n, j %= n;
	return cross(xx[i], yy[i], xx[j], yy[j]);
}

long long cross3(int i, int j, int k) {
	i %= n, j %= n, k %= n;
	return cross(xx[j] - xx[i], yy[j] - yy[i], xx[k] - xx[i], yy[k] - yy[i]);
}

int compare(int i, int j) {
	int i0 = i, i1 = i + 1, j0 = j, j1 = j + 1, tmp;
	long long c0, c1;

	if (cross2(i0, i1) > 0)
		tmp = i0, i0 = i1, i1 = tmp;
	if (cross2(j0, j1) > 0)
		tmp = j0, j0 = j1, j1 = tmp;
	c0 = cross3(i0, i1, j0), c1 = cross3(i0, i1, j1);
	if (c0 >= 0 && c1 >= 0)
		return -1;
	if (c0 <= 0 && c1 <= 0)
		return 1;
	c0 = cross3(j0, j1, i0), c1 = cross3(j0, j1, i1);
	if (c0 >= 0 && c1 >= 0)
		return 1;
	if (c0 <= 0 && c1 <= 0)
		return -1;
	return 0;
}

int main() {
	static int ii1[N], jj1[N], ii2[N], jj2[N];
	static char visible[N];
	int h, i, j, l, cnt1, cnt2, cnt;

	scanf("%d", &n);
	assert(n <= 190000);
	l = -1;
	for (i = 0; i < n; i++) {
		scanf("%d%d", &xx[i], &yy[i]);
		if (l == -1 || cross2(l, i) > 0)
			l = i;
	}
	i = l;
	cnt1 = cnt2 = 0;
	for (j = l; j < l + n; j++) {
		long long c = cross2(j, j + 1);

		if (c == 0) {
			if (cross2(i, j) == 0 && xx[i % n] > xx[(j + 1) % n])
				i = j + 1;
		} else if (c < 0) {
			if (cross2(j, i) <= 0 && cross2(i, j + 1) < 0)
				while (1) {
					if (cnt2 == 0) {
						ii1[cnt1] = i, jj1[cnt1] = j, cnt1++;
						i = j + 1;
						break;
					}
					if (compare(jj2[cnt2 - 1], j) <= 0)
						break;
					if (cross2(j + 1, ii2[cnt2 - 1]) < 0) {
						ii1[cnt1] = i, jj1[cnt1] = j, cnt1++;
						i = j + 1;
						break;
					}
					cnt2--;
					if (cross3(j, j + 1, ii2[cnt2]) <= 0) {
						ii1[cnt1] = i, jj1[cnt1] = j, cnt1++;
						i = ii2[cnt2];
						break;
					}
				}
		} else {
			if (cross2(j, i) >= 0 && cross2(i, j + 1) > 0) {
				while (1) {
					if (cnt1 == 0) {
						ii2[cnt2] = i, jj2[cnt2] = j, cnt2++;
						i = j + 1;
						break;
					}
					if (compare(jj1[cnt1 - 1], j) <= 0)
						break;
					if (cross2(j + 1, ii1[cnt1 - 1]) > 0) {
						ii2[cnt2] = i, jj2[cnt2] = j, cnt2++;
						i = j + 1;
						break;
					}
					cnt1--;
					if (cross3(j, j + 1, ii1[cnt1]) >= 0) {
						ii2[cnt2] = i, jj2[cnt2] = j, cnt2++;
						i = ii1[cnt1];
						break;
					}
				}
			}
		}
	}
	visible[i % n] = 1;
	for (h = 0; h < cnt1; h++)
		visible[ii1[h] % n] = 1;
	for (h = 0; h < cnt2; h++)
		visible[ii2[h] % n] = 1;
	cnt = 0;
	for (i = 0; i < n; i++)
		if (visible[i])
			cnt++;
	printf("%d\n", cnt);
	for (i = 0; i < n; i++)
		if (visible[i])
			printf("%d ", i + 1);
	printf("\n");
	return 0;
}

Compilation message

circuit.c: In function 'main':
circuit.c:48:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   48 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
circuit.c:52:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   52 |   scanf("%d%d", &xx[i], &yy[i]);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Verdict Execution time Memory Grader output
1 Correct 0 ms 212 KB Output is correct
2 Correct 1 ms 212 KB Output is correct
3 Correct 1 ms 340 KB Output is correct
4 Correct 2 ms 340 KB Output is correct
5 Correct 4 ms 340 KB Output is correct
6 Correct 4 ms 340 KB Output is correct
7 Correct 7 ms 468 KB Output is correct
8 Correct 3 ms 376 KB Output is correct
9 Correct 3 ms 340 KB Output is correct
10 Correct 3 ms 340 KB Output is correct
11 Correct 5 ms 364 KB Output is correct
12 Correct 4 ms 468 KB Output is correct
13 Correct 9 ms 524 KB Output is correct
14 Correct 9 ms 548 KB Output is correct
15 Correct 13 ms 644 KB Output is correct
16 Correct 24 ms 1064 KB Output is correct
17 Correct 31 ms 1096 KB Output is correct
18 Runtime error 1 ms 340 KB Execution killed with signal 6
19 Runtime error 1 ms 340 KB Execution killed with signal 6
20 Runtime error 1 ms 340 KB Execution killed with signal 6