最近点对HDU1007

利用二分的方法来计算,应该是说利用分治的方法吧! 刚开始感觉时间会爆 后来发现嘎嘎居然没有 ,嗨自己算错了时间:

#include <iostream>
#include<cstdio>
#include<string.h>
#include<algorithm>
#include<cmath>
using namespace std;
struct point
{
    double x,y;
    point (double a=0,double b=0)
    {
        x=a;y=b;
    }
};
struct point p[100005];
int  a[100005];
bool cmp1(point a,point b)
{
    if(a.x<b.x)return true;
    else return false;
}
bool cmp2(int a,int b)
{
    if(p[a].y<p[b].y)return true;
    else return false ;
}
double dist(point a,point b)
{
    return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}
double min_value(double a,double b){ return a>b?b:a;}
double find(int l,int r)
{
    if(l+1==r) return dist(p[l],p[r]);
    if(l+2==r)
	{
		double a1=dist(p[l],p[l+1]);
		double a2=dist(p[l+1],p[r]);
		double a3=dist(p[l],p[r]);
		a1= min_value(a1,min_value(a2,a3));
        return a1;
	}
	int mid,i,num,j;
    double ans;
    mid=(l+r)/2;
    num=0;
    ans=min_value(find(l,mid),find(mid+1,r));
    for(i=l;i<=r;i++)
        if(p[i].x>=p[mid].x-ans&&p[i].x<=p[mid].x+ans)
        a[num++]=i;
        sort(a,a+num,cmp2);
        for(i=0;i<num;i++)
        for(j=i+1;j<num;j++)
        {
            if(p[a[j]].y-p[a[i]].y>ans)break;
            ans=min_value(ans,dist(p[a[j]],p[a[i]]));
        }
        return ans;

}

int main()
{
    double x,y;
    int n,i;
    while(scanf("%d",&n)==1)
    {
        if(n==0)break;
        for(i=0;i<n;i++)
       {
           scanf("%lf%lf",&x,&y);
           p[i]=point(x,y);
       }
       sort(p,p+n,cmp1);
     printf("%.2lf
",find(0,n-1)/2);
    }

    return 0;
}