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답안 #951104

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
951104 2024-03-21T06:52:10 Z vjudge1 Printed Circuit Board (CEOI12_circuit) C++17
100 / 100
 31 ms 5744 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, ans[LEN];

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);
	if (L > 1) 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();
				}
			}
			else if (dir > 0) { // ccw
				if (cw && ccw > 0) {
					cw = 0;
					bv = i - 1;
					continue;
				}
				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;
				if (stack.empty() || p[stack.back()] < p[i]) 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);
			}
		}
	}

	for (const int& i : stack) ans[p[i].i] = 1;
	std::cout << stack.size() << '\n';
	for (int i = 1; i <= N; ++i)
		if (ans[i])
			std::cout << i << ' ';
}

Compilation message

circuit.cpp: In function 'int main()':
circuit.cpp:42:35: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   42 |   if (p[L] < p[i] || p[i] == p[L] && p[i].s() < p[L].s()) L = i;
      |                      ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
circuit.cpp:43:35: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   43 |   if (p[i] < p[R] || p[i] == p[R] && p[i].s() < p[R].s()) R = i;
      |                      ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

Subtask #1
100.0 / 100.0

# 결과 실행 시간 메모리 Grader output
1 Correct 1 ms 2396 KB Output is correct
2 Correct 1 ms 2396 KB Output is correct
3 Correct 1 ms 2396 KB Output is correct
4 Correct 1 ms 2512 KB Output is correct
5 Correct 2 ms 2396 KB Output is correct
6 Correct 2 ms 2396 KB Output is correct
7 Correct 3 ms 2516 KB Output is correct
8 Correct 2 ms 2396 KB Output is correct
9 Correct 2 ms 2396 KB Output is correct
10 Correct 2 ms 2396 KB Output is correct
11 Correct 2 ms 2396 KB Output is correct
12 Correct 3 ms 2396 KB Output is correct
13 Correct 5 ms 2396 KB Output is correct
14 Correct 5 ms 2512 KB Output is correct
15 Correct 7 ms 2392 KB Output is correct
16 Correct 12 ms 4440 KB Output is correct
17 Correct 15 ms 4444 KB Output is correct
18 Correct 31 ms 5744 KB Output is correct
19 Correct 29 ms 5716 KB Output is correct
20 Correct 27 ms 5724 KB Output is correct