Problem A : Quoit Design

#include<iostream>

#include<cstdio>

#include<vector>

#include<cmath>

#include<algorithm>

using namespace std;

struct point{

double x,y;

point(double xx = 0,double yy = 0){

x = xx;

y = yy;

}

void input(){

scanf("%lf%lf",&x,&y);

}

};

bool cmpx(point a,point b){

return a.x<b.x;

}

bool cmpy(point a,point b){

return a.y<b.y;

}

double dist(point a,point b){

return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));

}

vector<point> v;

double dfs(int l,int r){

vector<point> tem;

if(l+1==r)return dist(v[l],v[r]);

int mid = (l+r)>>1;

double d1 = dfs(l,mid);

double d2 = dfs(mid,r);

double d = min(d1,d2);

for(int i=0;;i++){

if(mid-i>=l&&abs(v[mid-i].x-v[mid].x)<=d){

tem.push_back(v[mid-i]);

}else{

break;

}

}

for(int i=1;;i++){

if(mid+i<=r&&abs(v[mid+i].x-v[mid].x)<=d){

tem.push_back(v[mid+i]);

}else{

break;

}

}

sort(tem.begin(),tem.end(),cmpy);

double minn = 1e10;

for(int i= 0;i<tem.size();i++){

for(int j=i+1;j<tem.size();j++){

if(tem[j].y-tem[i].y<=minn){

minn = min(minn,dist(tem[i],tem[j]));

}else{

break;

}

}

}

return min(d,minn);

}

int main(){

int N;

while(scanf("%d",&N)!=EOF&&N){

v.clear();

for(int i=0;i<N;i++){

point tem;tem.input();

v.push_back(tem);

}

sort(v.begin(),v.end(),cmpx);

printf("%.2lf\n",dfs(0,v.size()-1)/2);

}

}