Submission #1160109

#	Time	Username	Problem	Language	Result	Execution time	Memory
1160109		xnqs	Circle selection (APIO18_circle_selection)	C++20	7 / 100	3106 ms	596020 KiB

circle_selection

#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <utility>
#include <algorithm>
#include <cmath>
#include <unordered_map>
#include <unordered_set>

struct Circle {
	int64_t x, y, r, idx;
	Circle():
		x(0), y(0), r(0), idx(0) {}
	Circle(int64_t x, int64_t y, int64_t r, int64_t idx):
		x(x), y(y), r(r), idx(idx) {}

	bool operator == (const Circle& other) const {
		if (this->x!=other.x) return 0;
		if (this->y!=other.y) return 0;
		if (this->r!=other.r) return 0;
		if (this->idx!=other.idx) return 0;
		return 1;
	}
};

struct CircleHasher {
	std::size_t operator() (const Circle& c) const {
		return (c.x<<3) ^ (c.y<<5) ^ (c.r>>8) ^ (c.idx<<13);
	}
};

int64_t n;
std::vector<Circle> circles;
std::vector<int64_t> eliminator;

int64_t grid_size;
std::unordered_map<int64_t, std::unordered_map<int64_t, std::unordered_set<Circle, CircleHasher>>> grid;

inline int64_t euclid_dist(const Circle& a, const Circle& b) {
	return 1LL*(a.x-b.x)*(a.x-b.x) + 1LL*(a.y-b.y)*(a.y-b.y);
}

/*
	d(a,b) - a.r <= b.r
	sqrt((a.x-b.x)^2 + (a.y-b.y)^2) - a.r <= b.r
	sqrt((a.x-b.x)^2 + (a.y-b.y)^2) <= b.r + a.r
	(a.x-b.x)^2 + (a.y-b.y)^2 <= (b.r + a.r)^2
*/
inline bool intersect(const Circle& a, const Circle& b) {
	return euclid_dist(a,b) <= 1LL*(a.r+b.r)*(a.r+b.r);
}

void init_grid(int64_t size) {
	grid.clear();
	grid_size = size;
	for (int64_t i = 0; i < n; i++) {
		if (eliminator[circles[i].idx]) {
			continue;
		}

		grid[circles[i].x/size][circles[i].y/size].insert(circles[i]);
	}
}

int main() {
	std::ios_base::sync_with_stdio(false);
	std::cin.tie(NULL);
	std::cout.tie(NULL);

	std::cin >> n;
	for (int64_t i = 0, x, y, r; i < n; i++) {
		std::cin >> x >> y >> r;
		circles.emplace_back(x,y,r,i);
	}

	std::sort(circles.begin(),circles.end(),[](const Circle& a, const Circle& b) {
		return a.r > b.r;
	});

	eliminator.assign(n, 0);
	init_grid(4LL*circles[0].r);
	for (const auto& [x, y, r, idx] : circles) {
		if (4LL*r < grid_size/2) {
			init_grid(4LL*r);
		}
		if (eliminator[idx]) {
			continue;
		}

		eliminator[idx] = idx+1;

		//std::cout << idx << " " << grid_size << "\n";

		int64_t grid_x = x / grid_size;
		int64_t grid_y = y / grid_size;

		for (auto add_x : {-2, -1, 0, 1, 2}) {
			for (auto add_y : {-2, -1, 0, 1, 2}) {
				for (auto it = grid[grid_x+add_x][grid_y+add_y].begin(); it != grid[grid_x+add_x][grid_y+add_y].end();) {
					if (eliminator[it->idx]) {
						it = std::next(it);
						continue;
					}

					if (intersect(Circle(x,y,r,idx), *it)) {
						eliminator[it->idx] = idx+1;
						it = grid[grid_x+add_x][grid_y+add_y].erase(it);
					}
					else {
						it = std::next(it);
					}
				}
			}
		}
	}

	for (int64_t i = 0; i < n; i++) {
		std::cout << eliminator[i] << " ";
	}
	std::cout << "\n";
}

• Subtask 1: 7 / 7
• Subtask 2: 0 / 12
• Subtask 3: 0 / 15
• Subtask 4: 0 / 23
• Subtask 5: 0 / 30
• Subtask 6: 0 / 13