oj.uz

답안 #950437

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
950437 2024-03-20T10:09:06 Z vjudge1 Printed Circuit Board (CEOI12_circuit) C++17
100 / 100
 29 ms 2908 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);

	if (A > 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);
	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

# 결과 실행 시간 메모리 Grader output
1 Correct 0 ms 604 KB Output is correct
2 Correct 0 ms 604 KB Output is correct
3 Correct 1 ms 604 KB Output is correct
4 Correct 1 ms 604 KB Output is correct
5 Correct 2 ms 604 KB Output is correct
6 Correct 2 ms 604 KB Output is correct
7 Correct 3 ms 860 KB Output is correct
8 Correct 2 ms 604 KB Output is correct
9 Correct 2 ms 604 KB Output is correct
10 Correct 3 ms 604 KB Output is correct
11 Correct 2 ms 600 KB Output is correct
12 Correct 4 ms 860 KB Output is correct
13 Correct 5 ms 824 KB Output is correct
14 Correct 6 ms 1116 KB Output is correct
15 Correct 7 ms 1112 KB Output is correct
16 Correct 14 ms 1624 KB Output is correct
17 Correct 15 ms 1640 KB Output is correct
18 Correct 28 ms 2896 KB Output is correct
19 Correct 28 ms 2896 KB Output is correct
20 Correct 29 ms 2908 KB Output is correct