最近点对模版

#include <iostream>  #include <cstdio>  #include <cstring>  #include <cmath>  #include <algorithm>  using namespace std;  const double INF = 1e20;  const int N = 100005;    struct Point  {      double x;      double y;  }point[N];  int n;  int tmpt[N];    bool cmpxy(const Point& a, const Point& b)  {      if(a.x != b.x)          return a.x < b.x;      return a.y < b.y;  }    bool cmpy(const int& a, const int& b)  {      return point[a].y < point[b].y;  }    double min(double a, double b)  {      return a < b ? a : b;  }    double dis(int i, int j)  {      return sqrt((point[i].x-point[j].x)*(point[i].x-point[j].x)                  + (point[i].y-point[j].y)*(point[i].y-point[j].y));  }    double Closest_Pair(int left, int right)  {      double d = INF;      if(left==right)          return d;      if(left + 1 == right)          return dis(left, right);      int mid = (left+right)>>1;      double d1 = Closest_Pair(left,mid);      double d2 = Closest_Pair(mid+1,right);      d = min(d1,d2);      int i,j,k=0;      //分离出宽度为d的区间      for(i = left; i <= right; i++)      {          if(fabs(point[mid].x-point[i].x) <= d)              tmpt[k++] = i;      }      sort(tmpt,tmpt+k,cmpy);      //线性扫描      for(i = 0; i < k; i++)      {          for(j = i+1; j < k && point[tmpt[j]].y-point[tmpt[i]].y<d; j++)          {              double d3 = dis(tmpt[i],tmpt[j]);              if(d > d3)                  d = d3;          }      }      return d;  }      int main()  {      while(scanf("%d",&n)&&n)      {          if(n==0)              break;          for(int i = 0; i < n; i++)              scanf("%lf %lf",&point[i].x,&point[i].y);          sort(point,point+n,cmpxy);          printf("%.2lf\n",Closest_Pair(0,n-1)/2);// 除以2后为两点间的距离的一半      }      return 0;  }