Submission #372815

#	Time	Username	Problem	Language	Result	Execution time	Memory
372815		luciocf	Circle selection (APIO18_circle_selection)	C++14	0 / 100	1121 ms	19840 KiB

circle_selection

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int maxn = 3e5+10;

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

	bool operator<(const ll &o) const
	{
		return 1ll*y < o;
	}
} circle[maxn];

vector<vector<Circle>> V;

int R;

int ans[maxn];

bool comp1(Circle a, Circle b)
{
	if (a.x < b.x) 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)
{
	long double dx = a.x-b.x, dy = a.y-b.y, dr = a.r+b.r;

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

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

	int sign = (y < 0 ? 1 : -1);

	ll l_y = 1ll*y + 1ll*sign*(y%R) - 2ll*R, r_y = 1ll*y + 1ll*sign*(y%R) + 3ll*R;

	auto it = lower_bound(V[pos].begin(), V[pos].end(), l_y);
	for (; it != V[pos].end() && it->y <= 1ll*r_y; it++)
		if (intersect(circle[c], *it))
			ans[it->ind] = circle[c].ind;
}

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

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

	R = circle[1].r;

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

	for (int i = 1; i <= n; i++)
	{
		if (i == 1 || circle[i].x > circle[i-1].x)
			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;
		int x = circle[i].x, y = circle[i].y;

		int sign = (x < 0 ? 1 : -1);

		ll l_x = 1ll*x + 1ll*sign*(x%R) - 2ll*R, r_x = 1ll*x + 1ll*sign*(x%R) + 3ll*R;

		int p_l, p_r;

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

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

			if (1ll*V[mid][0].x >= 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 (1ll*V[mid][0].x <= 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 doit(int, int)':
circle_selection.cpp:46:6: warning: unused variable 'x' [-Wunused-variable]
   46 |  int x = circle[c].x, y = circle[c].y;
      |      ^
circle_selection.cpp: In function 'int main()':
circle_selection.cpp:86:24: warning: unused variable 'y' [-Wunused-variable]
   86 |   int x = circle[i].x, y = circle[i].y;
      |                        ^
circle_selection.cpp:61:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   61 |  scanf("%d", &n);
      |  ~~~~~^~~~~~~~~~
circle_selection.cpp:65:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   65 |   scanf("%d %d %d", &circle[i].x, &circle[i].y, &circle[i].r);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
circle_selection.cpp:92:12: warning: 'p_r' may be used uninitialized in this function [-Wmaybe-uninitialized]
   92 |   int p_l, p_r;
      |            ^~~
circle_selection.cpp:114:3: warning: 'p_l' may be used uninitialized in this function [-Wmaybe-uninitialized]
  114 |   for (int j = p_l; j <= p_r; j++)
      |   ^~~

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