【HDU 1007】 Quoit Design

【题目链接】

http://acm.hdu.edu.cn/showproblem.php?pid=1007

【算法】

答案为平面最近点对距离除以2

【代码】

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cerrno>
#include <clocale>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <limits>
#include <list>
#include <map>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <utility>
#include <vector>
#include <cwchar>
#include <cwctype>
#include <stack>
#include <limits.h>
using namespace std;
#define MAXN 100010
const double INF = 1e10;

struct info
{
        double x,y;
} a[MAXN];

int n,i;

inline bool cmpx(info a,info b)
{
        return a.x < b.x;
}
inline bool cmpy(info a,info b)
{
        return a.y < b.y;
}
inline double dist(info p,info q)
{
        return sqrt(abs(p.x - q.x) * abs(p.x - q.x) + abs(p.y - q.y) * abs(p.y - q.y));
}
inline double Closest_Pair(int l,int r)
{
        int i,j,mid,len = ;
        static info s[MAXN];
        double d;
        if (l == r) return INF;
        if (l +  == r) return dist(a[l],a[r]);
        mid = (l + r) >> ;
        d = min(Closest_Pair(l,mid),Closest_Pair(mid+,r));
        for (i = l; i <= r; i++)
        {
                if (abs(a[mid].x - a[i].x) <= d) s[++len] = a[i];
        }
        sort(s+,s+len+,cmpy);
        for (i = ; i <= len; i++)
        {
                for (j = i + ; j <= len && s[j].y - s[i].y <= d; j++)
                {
                        d = min(d,dist(s[i],s[j]));
                }
        }
        return d;
}

int main()
{

        while (scanf("%d",&n) && n)
        {
                for (i = ; i <= n; i++) scanf("%lf%lf",&a[i].x,&a[i].y);
                sort(a+,a+n+,cmpx);
                printf("%.2lf\n",Closest_Pair(,n) / 2.0);
        }

        return ;

}