zoj2107

来源：互联网发布：mysql 修改字段注释编辑：程序博客网时间：2024/06/06 04:15

# include <stdio.h># include <algorithm># include <math.h># define maxn 100009using namespace std;struct node{    double x,y;}vex[maxn],vex2[maxn];double min(double a,double b){    return a<b?a:b;}double dis(node a,node b){    return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));}int cmpx(node a,node b){    return a.x<b.x;}int cmpy(node a,node b){    return a.y<b.y;}double solve(int l,int r){    int m,i,j;    if(r==l+1)  return dis(vex[r],vex[l]);    if(r==l+2)  return min(dis(vex[l],vex[l+1]),min(dis(vex[l],vex[r]),dis(vex[l+1],vex[r])));    double d;    int mid=(r+l)/2;    d=min(solve(l,mid),solve(mid,r));    m=0;    for(i=l;i<=r;i++)    {        if(vex[i].x-vex[mid].x<=d&&vex[i].x-vex[mid].x>=-d)            vex2[m++]=vex[i];    }    sort(vex2,vex2+m,cmpy);    for(i=0;i<m;i++)        for(j=i+1;j<m;j++)    {        if(vex2[j].y-vex2[i].y>=d) break;        d=min(d,dis(vex2[i],vex2[j]));    }    return d;}int main (){    int n;    while(scanf("%d",&n)!=EOF)    {        if(n==0) break;        for(int i=0;i<n;i++)        {            scanf("%lf%lf",&vex[i].x,&vex[i].y);        }        sort(vex,vex+n,cmpx);        double ans=solve(0,n-1);        printf("%.2lf\n",ans/2);    }    return 0;}

空间最近点对模板有待改进关于分治时的以y的大小排序的改进算法导论上说可以一次性排序而不需要重新再排没看懂，，，，，，

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