#include <stdio.h>
#include <string.h>
#define N 200000
unsigned int X = 12345;
int rand_() {
return (X *= 3) >> 1;
}
long long cross2(int x1, int y1, int x2, int y2) {
return (long long) x1 * y2 - (long long) x2 * y1;
}
int xx[N], yy[N], ii[N * 2];
long long cross(int i, int j, int k) {
return cross2(xx[j] - xx[i], yy[j] - yy[i], xx[k] - xx[i], yy[k] - yy[i]);
}
int cmp(int h1, int h2) {
long long c = cross2(xx[ii[h1]], yy[ii[h1]], xx[ii[h2]], yy[ii[h2]]);
return c ? (c < 0 ? -1 : 1) : (h1 & 1) - (h2 & 1);
}
void sort(int *hh, int l, int r) {
while (l < r) {
int i = l, j = l, k = r, h_ = hh[l + rand_() % (r - l)], tmp;
while (j < k) {
int c = cmp(hh[j], h_);
if (c == 0)
j++;
else if (c < 0) {
tmp = hh[i], hh[i] = hh[j], hh[j] = tmp;
i++, j++;
} else {
k--;
tmp = hh[j], hh[j] = hh[k], hh[k] = tmp;
}
}
sort(hh, l, i);
l = k;
}
}
int iq[1 + N], pq[N], cnt, x_, y_;
int lt(int i, int j) {
int i0 = ii[i << 1 | 0], i1 = ii[i << 1 | 1], j0 = ii[j << 1 | 0], j1 = ii[j << 1 | 1];
return cross(i0, i1, j0) >= 0 && cross(i0, i1, j1) >= 0 || cross(j0, j1, i0) <= 0 && cross(j0, j1, i1) <= 0;
}
int p2(int p) {
return (p *= 2) > cnt ? 0 : (p < cnt && lt(iq[p + 1], iq[p]) ? p + 1 : p);
}
void pq_up(int i) {
int p, q, j;
for (p = pq[i]; (q = p / 2) && lt(i, j = iq[q]); p = q)
iq[pq[j] = p] = j;
iq[pq[i] = p] = i;
}
void pq_dn(int i) {
int p, q, j;
for (p = pq[i]; (q = p2(p)) && lt(j = iq[q], i); p = q)
iq[pq[j] = p] = j;
iq[pq[i] = p] = i;
}
void pq_add(int i) {
pq[i] = ++cnt, pq_up(i);
}
void pq_remove(int i) {
if (pq[i]) {
int j = iq[cnt--];
if (j != i)
pq[j] = pq[i], pq_up(j), pq_dn(j);
pq[i] = 0;
}
}
int main() {
static int hh[N * 2];
static char visible[N];
int n, n_, g, h, h_, i;
scanf("%d", &n);
for (i = 0; i < n; i++)
scanf("%d%d", &xx[i], &yy[i]);
n_ = 0;
for (i = 0; i < n; i++) {
long long c = cross2(xx[i], yy[i], xx[(i + 1) % n], yy[(i + 1) % n]);
if (c < 0) {
ii[i << 1 | 0] = i, ii[i << 1 | 1] = (i + 1) % n;
hh[n_++] = i << 1 | 0, hh[n_++] = i << 1 | 1;
} else if (c > 0) {
ii[i << 1 | 0] = (i + 1) % n, ii[i << 1 | 1] = i;
hh[n_++] = i << 1 | 0, hh[n_++] = i << 1 | 1;
}
}
sort(hh, 0, n_);
memset(visible, 1, n * sizeof *visible);
for (h = 0; h < n_; h++) {
h_ = hh[h];
x_ = xx[ii[h_]], y_ = yy[ii[h_]];
if ((h_ & 1) == 0)
pq_add(h_ >> 1);
else
pq_remove(h_ >> 1);
if (cnt) {
i = iq[1];
if (cross(ii[i << 1 | 0], ii[i << 1 | 1], ii[h_]) > 0)
visible[ii[h_]] = 0;
}
}
for (h = 0; h < n_; h = h_) {
int h1, i_;
h1 = hh[h], h_ = h, i_ = -1;
while (h_ < n_ && cross2(xx[ii[h1]], yy[ii[h1]], xx[ii[hh[h_]]], yy[ii[hh[h_]]]) == 0) {
i = ii[hh[h_++]];
if (i_ == -1 || xx[i_] > xx[i])
i_ = i;
}
for (g = h; g < h_; g++) {
i = ii[hh[g]];
if (i != i_)
visible[i] = 0;
}
}
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 'lt':
circuit.c:55:32: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
55 | return cross(i0, i1, j0) >= 0 && cross(i0, i1, j1) >= 0 || cross(j0, j1, i0) <= 0 && cross(j0, j1, i1) <= 0;
| ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
circuit.c: In function 'main':
circuit.c:97:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
97 | scanf("%d", &n);
| ^~~~~~~~~~~~~~~
circuit.c:99:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
99 | 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 |
340 KB |
Output is correct |
| 3 |
Correct |
2 ms |
384 KB |
Output is correct |
| 4 |
Correct |
2 ms |
340 KB |
Output is correct |
| 5 |
Correct |
7 ms |
596 KB |
Output is correct |
| 6 |
Correct |
8 ms |
596 KB |
Output is correct |
| 7 |
Correct |
15 ms |
852 KB |
Output is correct |
| 8 |
Correct |
6 ms |
468 KB |
Output is correct |
| 9 |
Correct |
7 ms |
584 KB |
Output is correct |
| 10 |
Correct |
7 ms |
596 KB |
Output is correct |
| 11 |
Correct |
10 ms |
640 KB |
Output is correct |
| 12 |
Correct |
10 ms |
840 KB |
Output is correct |
| 13 |
Correct |
21 ms |
1188 KB |
Output is correct |
| 14 |
Correct |
21 ms |
1444 KB |
Output is correct |
| 15 |
Correct |
27 ms |
1608 KB |
Output is correct |
| 16 |
Correct |
54 ms |
3100 KB |
Output is correct |
| 17 |
Correct |
73 ms |
3152 KB |
Output is correct |
| 18 |
Execution timed out |
105 ms |
5896 KB |
Time limit exceeded |
| 19 |
Execution timed out |
111 ms |
5912 KB |
Time limit exceeded |
| 20 |
Execution timed out |
155 ms |
6108 KB |
Time limit exceeded |
