分治法之最接近点对问题

/**
最近点对问题，时间复杂度为O(n*logn*logn)
*/
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
const double INF = 1e20;
const int N = 100005;

struct Point
{
    double x;
    double y;
}point[N];
int n;
int tmpt[N];

bool cmpxy(const Point& a, const Point& b)
{
    if(a.x != b.x)
        return a.x < b.x;
    return a.y < b.y;
}

bool cmpy(const int& a, const int& b)
{
    return point[a].y < point[b].y;
}

double min(double a, double b)
{
    return a < b ? a : b;
}

double dis(int i, int j)
{
    return sqrt((point[i].x-point[j].x)*(point[i].x-point[j].x)
                + (point[i].y-point[j].y)*(point[i].y-point[j].y));
}

double closest_pair(int left,int right)
{
	double d=INF
	if(left==right)
		return d;
	if(left+1=right)
		return dis(left,right);
	int mid=(left+right)/2;
	int d1=close_pair(left,mid);
	int d2=close_pair(mid+1,right);
	d=min(d1,d2);
	int i,j,k=0;
	for(i=left;i!=right;++i)
	{
		if(fabs(point[mid].x-point[i].x)<d)
			tmpt[k++]=i;
	}
	sort(tmpt,tmpt+k,cmpy);
	for(i=0;i!=k;++i)
	{
		for(j=i+1;j!=k&&point[j].y-point[i].y<d;++j)
		{
			double d3=dis(point[j],point[i]);
			if(d3<d)
				d=d3; 
		}
		
	}
	return d;
}



int main()
{
    while(true)
    {
        scanf("%d",&n);
        if(n==0)
            break;
        for(int i = 0; i < n; i++)
            scanf("%lf %lf",&point[i].x,&point[i].y);
        sort(point,point+n,cmpxy);
        printf("%.2lf\n",Closest_Pair(0,n-1)/2);//这个不是很明白，结果不是很正确啊，这个东西不是很正确，关键在于closet_pair的两个参数，对于是一维的话是很正确的，但是对于二维的话就不确定了
    }
    return 0;
}