poj3714

题目大意：

求两个集合点中，最近的点对的距离。

算法：

分治，和uva10245差不多，只不过这个多设个标志位，

 

悲剧：qsort超时，sort就ac。

 

#include <iostream>  
#include <algorithm>  
#include <cstdio>  
#include <cmath>  
#include <cstdlib>   

using namespace std; 

struct POINT 
{
	double x,y;
	int flag;
}point[200010],temp1[100010],temp2[100010];

double dis(POINT p1, POINT p2)
{
	if(p1.flag != p2.flag)
		return sqrt((p1.x - p2.x) * (p1.x - p2.x) + (p1.y - p2.y) * (p1.y - p2.y));
	else
		return 1e50;
}

bool cmp(POINT a, POINT b)
{
	return a.x < b.x;
}

double findMin(int l, int r)
{
	if (l == r)
	{
		return 1e50;
	}
	if (l == r - 1)
	{
		return dis(point[l], point[r]);
	}
	int mid =(l + r) >> 1;
	double tmp1 = findMin(l,mid);
	double tmp2 = findMin(mid + 1, r);
	double Mindis,tmp;
	int i,j;
	Mindis = tmp1 < tmp2 ? tmp1 : tmp2;
	int cnt1 = 0;
	int cnt2 = 0;
	for (i = mid; i >= l; -- i)
	{
		if ((point[mid].x - point[i].x) < Mindis)
		{
			temp1[cnt1 ++] = point[i];
		}
	}
	for (i = mid + 1; i <= r; ++ i)
	{
		if ((point[i].x - point[mid].x) < Mindis)
		{
			temp2[cnt2 ++] = point[i];
		}
	}
	for (i = 0; i < cnt1; ++ i)
	{
		for (j = 0; j < cnt2; ++ j)
		{
			tmp = dis(temp1[i], temp2[j]);
			if (tmp < Mindis)
			{
				Mindis = tmp;
			}
		}
	}
	return Mindis;

}
int main()
{
	int n,i,j;
	double minDis;
	scanf("%d", &j);
	while (j -- )
	{
		scanf("%d", &n);
		for (i = 0; i < n; ++ i)
		{
			scanf("%lf%lf", &point[i].x, &point[i].y);
			point[i].flag = 1;
		}
		for (i = n; i < 2 * n; ++ i)
		{
			scanf("%lf%lf", &point[i].x, &point[i].y);
			point[i].flag = 2;
		}
		n = n << 1;
		sort(point, point + n, cmp);
		minDis = findMin(0, n-1);
		
		printf("%.3lf\n", minDis);
	}
	return 0;
}