HDU-1007-Quoit Design

    #include <iostream>
    #include <cstdio>
    #include <cstring>
    #include <vector>
    #include <string>
    #include <algorithm>
    #include <queue>
    #include <cmath>
    using namespace std;
    struct point{
        double x,y;
        point(double x,double y):x(x),y(y){}
    };
    int n;
    vector<point> vp,tmp;
    bool cmpx(point a,point b){
        return a.x < b.x;
    }
    bool cmpy(point a,point b){
        return a.y < b.y;
    }
    double getDis(point a,point b){
        return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
    }
    double NearestPoint(int sta,int ed){
        if(sta+1==ed){
            return getDis(vp[sta],vp[ed]);
        }
        if(sta+2==ed){
            return min(min(getDis(vp[sta],vp[sta+1]),getDis(vp[sta+1],vp[ed])),getDis(vp[sta],vp[ed]));
        }
        int mid = (sta+ed)>>1;
        double res = min(NearestPoint(sta,mid),NearestPoint(mid+1,ed));
        tmp.clear();
        for(int i = sta;i <= ed; i++){
            if(fabs(vp[i].x-vp[mid].x)<res){
                tmp.push_back(vp[i]);
            }
        }
        sort(tmp.begin(),tmp.end(),cmpy);
        for(int i = 0; i < tmp.size(); i++){
            for(int j = i+1; j < tmp.size() && tmp[j].y-tmp[i].y<=res; j++){
                if(getDis(tmp[i],tmp[j]) < res)
                    res = getDis(tmp[i],tmp[j]);
            }
        }
        return res;

    }
    int main(){
        while(cin >> n && n){
            vp.clear();
            for(int i = 0; i < n; i++){
                double a,b;
                scanf("%lf%lf",&a,&b);
                vp.push_back(point(a,b));
            }
            sort(vp.begin(),vp.end(),cmpx);
            printf("%.2f\n",NearestPoint(0,vp.size()-1)/2);

        }
        return 0;
    }