Submission #372830

#	Time	Username	Problem	Language	Result	Execution time	Memory
372830		luciocf	Circle selection (APIO18_circle_selection)	C++14	35 / 100	741 ms	67780 KiB

circle_selection

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int maxn = 3e5+10;
const int add = 1e9;

ll R;

struct Circle
{
	ll x, y, r;
	int ind;

	bool operator<(const ll &o) const
	{
		return y/R < o;
	}
} circle[maxn];

vector<vector<Circle>> V;

int ans[maxn];

bool comp1(Circle a, Circle b)
{
	if (a.x/R == b.x/R) return a.y < b.y;
	return a.x < b.x;
}

bool comp2(Circle a, Circle b)
{
	if (a.r == b.r) return a.ind < b.ind;
	return a.r > b.r;
}

bool intersect(Circle a, Circle b)
{
	ll dx = a.x-b.x, dy = a.y-b.y, dr = a.r+b.r;

	return dx*dx + dy*dy <= dr*dr;
}

void rescale(void)
{
	vector<vector<Circle>> aux;

	for (int i = 0; i < V.size(); i++)
	{
		ll mn = 1e18, mx = 0;

		for (auto c: V[i])
		{
			mn = min(mn, c.x/R);
			mx = max(mx, c.x/R);
		}

		ll med = mn;
		for (auto c: V[i])
			if (c.x/R != mn && c.x/R != mx)
				med = c.x/R;

		if (aux.size() == 0 || mn > aux.back()[0].x/R)
			aux.push_back(vector<Circle>());

		for (auto c: V[i])
			if (c.x/R == mn)
				aux.back().push_back(c);

		if (med > mn)
		{
			aux.push_back(vector<Circle>());

			for (auto c: V[i])
				if (c.x/R == med)
					aux.back().push_back(c);
		}

		if (mx > med)
		{
			aux.push_back(vector<Circle>());

			for (auto c: V[i])
				if (c.x/R == mx)
					aux.back().push_back(c);
		}
	}

	swap(aux, V);
}

void doit(int pos, int c)
{
	ll y = circle[c].y;

	ll l_y = y/R - 2, r_y = y/R + 3;

	auto it = lower_bound(V[pos].begin(), V[pos].end(), l_y);
	for (; it != V[pos].end() && it->y/R <= r_y; it++)
		if (intersect(circle[c], *it) && !ans[it->ind])
			ans[it->ind] = circle[c].ind;
}

int main(void)
{
	int n;
	scanf("%d", &n);

	for (int i = 1; i <= n; i++)
	{
		scanf("%lld %lld %lld", &circle[i].x, &circle[i].y, &circle[i].r);
		circle[i].x += add, circle[i].y += add;
		circle[i].ind = i;

		R = max(R, circle[i].r);
	}

	sort(circle+1, circle+n+1, comp1);

	for (int i = 1; i <= n; i++)
	{
		if (i == 1 || circle[i].x/R > circle[i-1].x/R)
			V.push_back(vector<Circle>());

		V.back().push_back(circle[i]);
	}

	sort(circle+1, circle+n+1, comp2);

	for (int i = 1; i <= n; i++)
	{
		if (ans[circle[i].ind]) continue;

		while (circle[i].r < R/2)
		{
			R /= 2;
			rescale();
		}

		ll x = circle[i].x;

		ll l_x = x/R - 2, r_x = x/R + 3;

		int p_l, p_r;

		int ini = 0, fim = (int)V.size()-1;

		while (ini <= fim)
		{
			int mid = (ini+fim)>>1;

			if (V[mid][0].x/R >= l_x) p_l = mid, fim = mid-1;
			else ini = mid+1;
		}

		ini = 0, fim = (int)V.size()-1;

		while (ini <= fim)
		{
			int mid = (ini+fim)>>1;

			if (V[mid][0].x/R <= r_x) p_r = mid, ini = mid+1;
			else fim = mid-1;
		}

		for (int j = p_l; j <= p_r; j++)
			doit(j, i);
	}

	for (int i = 1; i <= n; i++)
		printf("%d ", ans[i]);
	printf("\n");
}

Compilation message (stderr)

circle_selection.cpp: In function 'void rescale()':
circle_selection.cpp:50:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<Circle> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   50 |  for (int i = 0; i < V.size(); i++)
      |                  ~~^~~~~~~~~~
circle_selection.cpp: In function 'int main()':
circle_selection.cpp:109:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  109 |  scanf("%d", &n);
      |  ~~~~~^~~~~~~~~~
circle_selection.cpp:113:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  113 |   scanf("%lld %lld %lld", &circle[i].x, &circle[i].y, &circle[i].r);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
circle_selection.cpp:146:12: warning: 'p_r' may be used uninitialized in this function [-Wmaybe-uninitialized]
  146 |   int p_l, p_r;
      |            ^~~
circle_selection.cpp:168:3: warning: 'p_l' may be used uninitialized in this function [-Wmaybe-uninitialized]
  168 |   for (int j = p_l; j <= p_r; j++)
      |   ^~~

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