Cod sursa(job #545878)

Utilizator CipaFlorescu Ciprian Cipa Data 4 martie 2011 03:03:55
Problema Cele mai apropiate puncte din plan Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.63 kb
#include<cstdio>
#include<math.h>
#include<stdlib.h>

struct point{
int x,y;};

typedef struct point Point;
double distance(Point a, Point b)
{
	double d;
	d = pow((double)(a.x - b.x),2.0);
	d += pow((double)(a.y - b.y),2.0);
	return sqrt(d);  
}

int comparePoints(const void * a, const void * b)
{
	return ((Point*)a)->x - ((Point*)b)->x;
}

double findLowest(Point * p[],int length)
{
	double lowest = 2000000000;
	for(int i = 0; i < length;i++)
	{
		for(int j = i+1;j<=i+7 && j <= length;j++)
		{
			double d = distance(*p[i],*p[j]);
			if(d<lowest)
				lowest = d;
		}
	}
	
	return lowest;
}

double lowestDistance(Point p[],int start, int end)
{
	int middle = (start + end)/2;
	int middleX = p[middle].x;
	double d;
	double lowest;
	lowest = distance(p[start],p[start+1]);
	if(end - start <= 3)
	{
		for(int i = start; i<end-1;i++)
			for(int j = i + 1; j < end;j++)
			{
				d = distance(p[i],p[j]);
				if(d < lowest)
					lowest = d;
			}
			
		return lowest;
	}
	double d1 = lowestDistance(p,start,middle);
	double d2 = lowestDistance(p,middle, end);
	
	if(d1 < d2)
		lowest = d1;
	else 
		lowest = d2;
		
	Point *r[end-start];
	int j = -1;
	for(int i = start; i < end;i++)
		if(abs(middleX-p[i].x) <= lowest)
			r[++j] = &p[i];
			
	double lowest2 = findLowest(r,j);
	if(lowest2 < lowest)
		return lowest2;
	return lowest;
}

int main()
{
	freopen("cmap.in","r",stdin);
	freopen("cmap.out","w",stdout);
	int n;
	scanf("%d",&n);
	Point points[n];
	
	for(int i=0;i<n;i++)
	{
		int x,y;
		scanf("%d %d",&x,&y);
		points[i].x = x;
		points[i].y = y;
	}
	qsort(&points,n,sizeof(Point),comparePoints);
	
	double d = lowestDistance(points,0,n);
	printf("%5.6f",d);
}