#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <cassert>
#include <vector>
typedef long long ll;
//typedef double ld;
const ll INF = 1e17;
const int LEN = 2e5 + 1;
int N;
bool V[LEN];
struct Pos {
int x, y, i;
Pos(int X = 0, int Y = 0, int I = 0) : x(X), y(Y), i(I) {}
bool operator == (const Pos& p) const { return x == p.x && y == p.y; }
bool operator != (const Pos& p) const { return x != p.x || y != p.y; }
ll operator * (const Pos& p) const { return { (ll)x * p.x + (ll)y * p.y }; }
ll operator / (const Pos& p) const { return { (ll)x * p.y - (ll)y * p.x }; }
bool operator < (const Pos& p) const { return *this / p > 0; }
bool operator <= (const Pos& p) const { return *this / p >= 0; }
Pos operator + (const Pos& p) const { return { x + p.x, y + p.y }; }
Pos operator - (const Pos& p) const { return { x - p.x, y - p.y }; }
ll Euc() const { return (ll)x * x + (ll)y * y; }
friend std::istream& operator >> (std::istream& is, Pos& p) {
is >> p.x >> p.y;
return is;
}
friend std::ostream& operator << (std::ostream& os, const Pos& p) {
os << p.x << " " << p.y;
return os;
}
}; const Pos O = { 0, 0 };
std::vector<Pos> C, H;
ll cross(const Pos& d1, const Pos& d2, const Pos& d3) { return (d2 - d1) / (d3 - d2); }
int ccw(const Pos& d1, const Pos& d2, const Pos& d3) {
ll ret = cross(d1, d2, d3);
return !ret ? 0 : ret > 0 ? 1 : -1;
}
ll area(const std::vector<Pos>& H) {
ll ret = 0;
int sz = H.size();
for (int i = 0; i < sz; i++) {
Pos cur = H[i], nxt = H[(i + 1) % sz];
ret += cross(O, cur, nxt);
}
return ret;
}
bool norm(std::vector<Pos>& H) {
if (area(H) > 0) {
std::reverse(H.begin(), H.end());
return 1;
}
return 0;
}
int invisible(const Pos& p1, const Pos& p2, const Pos& t) {
if (p1 / t == 0 && p1.Euc() <= t.Euc()) return 1;
if (p2 / t == 0 && p2.Euc() <= t.Euc()) return 1;
return ccw(O, p1, t) < 0 && ccw(O, p2, t) > 0 && ccw(p1, p2, t) > 0;
}
std::vector<int> stack;
void solve() {
std::cin.tie(0)->sync_with_stdio(0);
std::cout.tie(0);
memset(V, 0, sizeof V);
std::cin >> N;
H.resize(N);
for (int i = 0; i < N; i++) std::cin >> H[i], H[i].i = i + 1;
norm(H);//normalization cw
int r = 0, l = 0;
ll LMIN = H[0].Euc(), RMIN = H[0].Euc();
for (int i = 0; i < N; i++) {
if (H[r] / H[i] < 0 ||
(H[r] / H[i] == 0 && RMIN > H[i].Euc())) {
r = i, RMIN = H[i].Euc();
}
if (H[l] / H[i] > 0 ||
(H[l] / H[i] == 0 && LMIN > H[i].Euc())) {
l = i, LMIN = H[i].Euc();
}
}
stack.clear();
stack.push_back(r);
V[H[r].i] = 1;
bool fvis = 1, bvis = 1, rvs = 0;
for (int i = r; i < r + N; i++) {
if (i % N == l) break;
if (fvis && bvis) {
int CCW = ccw(H[(i - 1 + N) % N], H[i % N], H[(i + 1) % N]);
if (H[i % N] / H[(i + 1) % N] < 0) {//move backward
if (!rvs && CCW < 0) {
rvs = 1;
fvis = 0;
continue;
}
rvs = 1;
while (stack.size() && invisible(H[i % N], H[(i + 1) % N], H[stack.back() % N]))
stack.pop_back();
}
else if (H[i % N] / H[(i + 1) % N] == 0) {//move vertical
if (H[i % N].Euc() > H[(i + 1) % N].Euc()) {
//rvs = 0;
if (stack[stack.size() - 1] == i) stack.pop_back();
if (stack.size() < 1 || H[stack.back() % N] / H[(i + 1) % N] > 0)
stack.push_back(i + 1);
}
}
else if (H[i % N] / H[(i + 1) % N] > 0) {//move forward
if (rvs && CCW > 0) {
stack.push_back(i);
rvs = 0;
bvis = 0;
continue;
}
rvs = 0;
if (stack.size() < 1 || H[stack.back() % N] / H[(i + 1) % N] > 0)
stack.push_back(i + 1);
}
}
else if (!fvis) {
if (H[stack.back() % N] / H[(i + 1) % N] > 0) {
rvs = 0;
fvis = 1;
stack.push_back(i + 1);
}
}
else if (!bvis) {
if (H[stack.back() % N] / H[(i + 1) % N] < 0) {
stack.pop_back();
rvs = 1;
bvis = 1;
while (stack.size() && invisible(H[i % N], H[(i + 1) % N], H[stack.back() % N]))
stack.pop_back();
}
}
}
for (const int& i : stack) V[H[i % N].i] = 1;
std::cout << stack.size() << "\n";
for (int i = 1; i <= N; i++) if (V[i]) std::cout << i << " ";
return;
}
int main() { solve(); return 0; }//boj3303 Printed Circuit Board
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
856 KB |
Output is correct |
| 2 |
Incorrect |
1 ms |
604 KB |
Output isn't correct |
| 3 |
Correct |
2 ms |
604 KB |
Output is correct |
| 4 |
Correct |
2 ms |
604 KB |
Output is correct |
| 5 |
Incorrect |
2 ms |
604 KB |
Output isn't correct |
| 6 |
Incorrect |
2 ms |
604 KB |
Output isn't correct |
| 7 |
Incorrect |
4 ms |
860 KB |
Output isn't correct |
| 8 |
Incorrect |
2 ms |
604 KB |
Output isn't correct |
| 9 |
Incorrect |
2 ms |
604 KB |
Output isn't correct |
| 10 |
Incorrect |
2 ms |
604 KB |
Output isn't correct |
| 11 |
Incorrect |
2 ms |
604 KB |
Output isn't correct |
| 12 |
Incorrect |
3 ms |
860 KB |
Output isn't correct |
| 13 |
Incorrect |
5 ms |
860 KB |
Output isn't correct |
| 14 |
Incorrect |
6 ms |
1116 KB |
Output isn't correct |
| 15 |
Incorrect |
7 ms |
1116 KB |
Output isn't correct |
| 16 |
Incorrect |
14 ms |
1628 KB |
Output isn't correct |
| 17 |
Incorrect |
20 ms |
1624 KB |
Output isn't correct |
| 18 |
Incorrect |
27 ms |
2908 KB |
Output isn't correct |
| 19 |
Incorrect |
27 ms |
2904 KB |
Output isn't correct |
| 20 |
Incorrect |
29 ms |
2908 KB |
Output isn't correct |
