Submission #951034

# Submission time Handle Problem Language Result Execution time Memory
951034 2024-03-21T04:47:41 Z vjudge1 Printed Circuit Board (CEOI12_circuit) C++17
95 / 100
27 ms 5084 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);
	std::sort(ret.begin(), ret.end());
	ret.erase(unique(ret.begin(), ret.end()), 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;
      |                      ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
# Verdict Execution time Memory Grader output
1 Incorrect 1 ms 344 KB Output isn't correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 1 ms 604 KB Output is correct
5 Correct 2 ms 2652 KB Output is correct
6 Correct 2 ms 2652 KB Output is correct
7 Correct 3 ms 2652 KB Output is correct
8 Correct 2 ms 2652 KB Output is correct
9 Correct 2 ms 2652 KB Output is correct
10 Correct 2 ms 2652 KB Output is correct
11 Correct 2 ms 2652 KB Output is correct
12 Correct 3 ms 2680 KB Output is correct
13 Correct 5 ms 2652 KB Output is correct
14 Correct 5 ms 2652 KB Output is correct
15 Correct 6 ms 2684 KB Output is correct
16 Correct 14 ms 4700 KB Output is correct
17 Correct 15 ms 4736 KB Output is correct
18 Correct 24 ms 4956 KB Output is correct
19 Correct 25 ms 5000 KB Output is correct
20 Correct 27 ms 5084 KB Output is correct