HDU - 1007 Quoit Design

传送门

平面最近点对模板。

//Achen
#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<vector>
#include<cstdio>
#include<queue>
#include<cmath>
const int N=1e5+7;
typedef long long LL;
typedef double db;
using namespace std;
int T,n;

template<typename T>void read(T &x)  {
    char ch=getchar(); x=0; T f=1;
    while(ch!='-'&&(ch<'0'||ch>'9')) ch=getchar();
    if(ch=='-') f=-1,ch=getchar();
    for(;ch>='0'&&ch<='9';ch=getchar()) x=x*10+ch-'0'; x*=f;
}

struct pt {
    db x,y;
}p[N],tp[N];

bool cmp(const pt&A,const pt&B) { return A.x<B.x||(A.x==B.x&&A.y<B.y); }
bool cmpy(const pt&A,const pt&B) { return A.y<B.y; }
db sqr(db x) {return x*x;}
db dis(pt A,pt B) { return sqrt(sqr(A.x-B.x)+sqr(A.y-B.y)); }

db solve(int l,int r) {
    db d=1e18;
    if(l>=r) return d;
    if(l+1==r) return dis(p[l],p[r]);
    int mid=((l+r)>>1);
    d=min(d,solve(l,mid)); 
    d=min(d,solve(mid+1,r));
    int k=0;
    for(int i=l;i<=r;i++) 
        if(fabs(p[i].x-p[mid].x)<=d) tp[++k]=p[i];
    sort(tp+1,tp+k+1,cmpy);
    for(int i=1;i<=k;i++) 
        for(int j=i+1;j<=k&&tp[j].y-tp[i].y<d;j++) 
            d=min(d,dis(tp[i],tp[j]));
    return d;
}

int main() {
#ifdef DEBUG
    freopen(".in","r",stdin);
    freopen(".out","w",stdout);
#endif
    for(;;) {
        read(n);
        if(!n) break;
        for(int i=1;i<=n;i++) scanf("%lf%lf",&p[i].x,&p[i].y);
        sort(p+1,p+n+1,cmp);
        printf("%.2lf\n",solve(1,n)/2);
    }
    return 0;
}