HDU 1007 Quoit Design

平面最近点对模板题。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#define maxn 100500
#define inf 1e20
using namespace std;
struct point
{
    double x,y;
}p[maxn];
int n,stack[maxn];
bool cmp(int a,int b)
{
    return p[a].y<p[b].y;
}
bool cmpp(point a,point b)
{
    if (a.x!=b.x) return a.x<b.x;
    return a.y<b.y;
}
double dis(int a,int b)
{
    return sqrt((p[a].x-p[b].x)*(p[a].x-p[b].x)+(p[a].y-p[b].y)*(p[a].y-p[b].y));
}
double mn(double x,double y)
{
    if (x>y) return y;
    return x;
}
double find(int left,int right)
{
    if (left==right) return inf;
    if (left+1==right) return dis(left,right);
    int mid=(left+right)>>1;
    double now=mn(find(left,mid),find(mid,right));
    int top=0;
    for (int i=left;i<=right;i++)
    {
        if (fabs(p[i].x-p[mid].x)<=now)
            stack[++top]=i;
    }
    sort(stack+1,stack+top+1,cmp);
    for (int i=1;i<=top;i++)
        for (int j=i+1;j<=top && p[stack[j]].y-p[stack[i]].y<now;j++)
        {
            double then=dis(stack[i],stack[j]);
            now=mn(now,then);
        }
    return now;
}
void work()
{
    for (int i=1;i<=n;i++)
        scanf("%lf%lf",&p[i].x,&p[i].y);
    sort(p+1,p+n+1,cmpp);
    printf("%.2lf
",find(1,n)/2);
}
int main()
{
    while (scanf("%d",&n)==1)
    {
        if (n==0) break;
        else work();
    }
    return 0;
}