답안 #951031

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
951031 2024-03-21T04:45:56 Z vjudge1 Printed Circuit Board (CEOI12_circuit) C++17
10 / 100
32 ms 5244 KB
#include <iostream>
#include <algorithm>
#include <vector>

typedef long long ll;
const int LEN = 200'001;

struct Pos {
	ll x, y;
	int i;
	ll s() const { return x * x + y * y; }
	bool operator<(const Pos& r) const { return y * r.x < r.y * x; }
	bool operator==(const Pos& r) const { return y * r.x == r.y * x; }
	friend std::istream& operator>>(std::istream& is, Pos& p) { is >> p.x >> p.y; return is; }
} O = { 0, 0 }, p[LEN];
ll cross(const Pos& p1, const Pos& p2, const Pos& p3) { return (p2.x - p1.x) * (p3.y - p2.y) - (p2.y - p1.y) * (p3.x - p2.x); }
ll ccw(const Pos& p1, const Pos& p2, const Pos& p3) {
	ll ret = cross(p1, p2, p3);
	return ret < 0 ? -1 : !!ret;
}

bool invisible(const Pos& p1, const Pos& p2, const Pos& t) {
	return ccw(O, p1, t) <= 0 && ccw(O, p2, t) >= 0 && ccw(p1, p2, t) >= 0;
}

int N, L, R;

int main() {
	std::cin.tie(0)->sync_with_stdio(0);
	std::cin >> N >> p[0];
	p[0].i = 1;
	ll area = 0;
	for (int i = 1; i < N; ++i) {
		std::cin >> p[i];
		p[i].i = i + 1;
		area += cross(O, p[i - 1], p[i]);
	}
	area += cross(O, p[N - 1], p[0]);
	if (area > 0) std::reverse(p, p + N);
	for (int i = 1; i < N; ++i) {
		if (p[L] < p[i] || p[i] == p[L] && p[i].s() < p[L].s()) L = i;
		if (p[i] < p[R] || p[i] == p[R] && p[i].s() < p[R].s()) R = i;
	}
	std::rotate(p, p + R, p + N);
	L = (L - R + N) % N;

	// std::cout << R << ' ' << L << '\n';
	// std::cout << p[0].i << ' ' << p[L].i << '\n';

	std::vector<int> stack; // monotonic, ccw order
	stack.push_back(0);
	stack.push_back(1);

	for (int i = 2, fv = -1, bv = -1, cw = 0; i <= L; ++i) {
		// j -> i
		ll dir = cross(O, p[i - 1], p[i]);
		ll ccw = cross(p[i - 2], p[i - 1], p[i]);

		if (!~fv && !~bv) {
			if (dir < 0) { // cw
				if (!cw && ccw < 0) {
					cw = 1;
					fv = i - 1;
					continue;
				}
				cw = 1;
				while (stack.size() && invisible(p[i - 1], p[i], p[stack.back()])) stack.pop_back();
			}
			else if (dir == 0) {
				if (p[i].s() < p[i - 1].s()) {
					if (stack.back() == i - 1) stack.pop_back();
					if (stack.empty() || p[stack.back()] < p[i]) stack.push_back(i);
				}
			}
			else if (dir > 0) { // ccw
				if (cw && ccw > 0) {
					cw = 0;
					bv = i - 1;
					continue;
				}
				//if (!stack.empty() && cw && p[stack.back()] < p[i - 1]) stack.push_back(i - 1);
				cw = 0;
				if (stack.empty() || p[stack.back()] < p[i]) stack.push_back(i);
			}
		}
		else if (~fv) {
			if (p[fv] < p[i]) {
				cw = 0;
				fv = -1;
				stack.push_back(i);
			}
		}
		else if (~bv) {
			if (p[i] < p[bv]) {
				cw = 1;
				bv = -1;
				while (stack.size() && invisible(p[i - 1], p[i], p[stack.back()])) stack.pop_back();
				if (stack.empty() || p[stack.back()] < p[i]) stack.push_back(i);
			}
		}
	}

	std::vector<int> ret;
	for (const int& i : stack) ret.push_back(p[i].i);
	ret.erase(unique(ret.begin(), ret.end()), ret.end());
	std::sort(ret.begin(), ret.end());
	std::cout << ret.size() << '\n';
	for (const int& i : ret) std::cout << i << ' ';
}

Compilation message

circuit.cpp: In function 'int main()':
circuit.cpp:41:35: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   41 |   if (p[L] < p[i] || p[i] == p[L] && p[i].s() < p[L].s()) L = i;
      |                      ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
circuit.cpp:42:35: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   42 |   if (p[i] < p[R] || p[i] == p[R] && p[i].s() < p[R].s()) R = i;
      |                      ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
# 결과 실행 시간 메모리 Grader output
1 Incorrect 0 ms 348 KB Output isn't correct
2 Incorrect 0 ms 348 KB Output isn't correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 1 ms 856 KB Output is correct
5 Incorrect 2 ms 2652 KB Output isn't correct
6 Incorrect 2 ms 2652 KB Output isn't correct
7 Incorrect 4 ms 2652 KB Output isn't correct
8 Incorrect 2 ms 2652 KB Output isn't correct
9 Incorrect 2 ms 2648 KB Output isn't correct
10 Incorrect 2 ms 2648 KB Output isn't correct
11 Incorrect 2 ms 2652 KB Output isn't correct
12 Incorrect 3 ms 2688 KB Output isn't correct
13 Incorrect 4 ms 2652 KB Output isn't correct
14 Incorrect 5 ms 2476 KB Output isn't correct
15 Incorrect 6 ms 2652 KB Output isn't correct
16 Incorrect 13 ms 4700 KB Output isn't correct
17 Incorrect 13 ms 4736 KB Output isn't correct
18 Incorrect 30 ms 4948 KB Output isn't correct
19 Incorrect 31 ms 4948 KB Output isn't correct
20 Incorrect 32 ms 5244 KB Output isn't correct