oj.uz

Submission #950700

# Submission time Handle Problem Language Result Execution time Memory
950700 2024-03-20T15:30:13 Z vjudge1 Printed Circuit Board (CEOI12_circuit) C++17
100 / 100
 30 ms 5468 KB 
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <vector>
#include <cassert>
typedef long long ll;
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) {}
	ll operator / (const Pos& p) const { return { (ll)x * p.y - (ll)y * p.x }; }
	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> 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) {
	ll A = area(H);
	assert(A);
	if (A > 0) { std::reverse(H.begin(), H.end()); return 1; }
	return 0;
}
bool 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);
	std::cin >> N;
	H.resize(N);
	for (int i = 0; i < N; i++) std::cin >> H[i], H[i].i = i + 1;
	norm(H);//normalize 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);

	bool fvis = 1, bvis = 1, rvs = 0;
	for (int i = r; i < r + N; i++) {
		if (i % N == l) break;
		Pos& pre = H[(i - 1 + N) % N], cur = H[i % N], nxt = H[(i + 1) % N];
		if (fvis && bvis) {
			ll DIR = cur / nxt;
			int CCW = ccw(pre, cur, nxt);
			if (DIR < 0) {//move backward
				if (!rvs && CCW < 0) {
					rvs = 1;
					fvis = 0;
					continue;
				}
				rvs = 1;
				while (stack.size() && invisible(cur, nxt, H[stack.back()])) stack.pop_back();
			}
			else if (!DIR) {//move vertical
				if (cur.Euc() > nxt.Euc()) {
					if (stack.size() && stack.back() == i % N) stack.pop_back();
					if (stack.size() < 1 || H[stack.back()] / nxt > 0) stack.push_back((i + 1) % N);
				}
			}
			else if (DIR > 0) {//move forward
				if (rvs && CCW > 0) {
					stack.push_back(i % N);
					rvs = 0;
					bvis = 0;
					continue;
				}
				if (stack.size() && rvs && H[stack.back()] / cur > 0) stack.push_back(i % N);
				rvs = 0;
				if (stack.size() < 1 || H[stack.back()] / nxt > 0) stack.push_back((i + 1) % N);
			}
		}
		else if (!fvis) {
			if (H[stack.back()] / nxt > 0) {
				rvs = 0;
				fvis = 1;
				stack.push_back((i + 1) % N);
			}
		}
		else if (!bvis) {
			if (H[stack.back()] / nxt < 0) {
				stack.pop_back();
				rvs = 1;
				bvis = 1;
				while (stack.size() && invisible(cur, nxt, H[stack.back()])) stack.pop_back();
			}
		}
	}

	memset(V, 0, sizeof V);
	for (const int& i : stack) V[H[i].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

Subtask #1
100.0 / 100.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 604 KB Output is correct
2 Correct 1 ms 600 KB Output is correct
3 Correct 1 ms 604 KB Output is correct
4 Correct 1 ms 536 KB Output is correct
5 Correct 2 ms 860 KB Output is correct
6 Correct 2 ms 860 KB Output is correct
7 Correct 4 ms 1116 KB Output is correct
8 Correct 3 ms 860 KB Output is correct
9 Correct 2 ms 856 KB Output is correct
10 Correct 2 ms 856 KB Output is correct
11 Correct 2 ms 860 KB Output is correct
12 Correct 3 ms 1076 KB Output is correct
13 Correct 5 ms 1372 KB Output is correct
14 Correct 6 ms 1372 KB Output is correct
15 Correct 7 ms 1628 KB Output is correct
16 Correct 14 ms 2908 KB Output is correct
17 Correct 15 ms 3160 KB Output is correct
18 Correct 27 ms 5360 KB Output is correct
19 Correct 28 ms 5468 KB Output is correct
20 Correct 30 ms 5468 KB Output is correct