今天看《计算机算法设计与分析》第二版里的最近点对,
按着写了,可以过hud的,不能过zoj的,郁闷死了。
查了半天,发现书上印错了,33页第一行第一个Y改成X
下面是可以过zoj的代码:
#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <math.h>
#include <string.h>
using namespace std;
#define N 120005
struct point
{
double x,y;
int id;
}aa[N],bb[N],cc[N];
bool cmp_x(point a,point b)
{
return a.x<b.x;
}
bool cmp_y(point a,point b)
{
return a.y<b.y;
}
double dis(point a,point b)
{
double dx=a.x-b.x,dy=a.y-b.y;
return sqrt(dx*dx+dy*dy);
}
void merge(point c[],point d[],int l,int m,int r)
{
int i=l,j=m+1,k=l;
while(i<=m&&j<=r)
if(c[i].y<=c[j].y)d[k++]=c[i++];
else d[k++]=c[j++];
if(i>m)
while(j<=r)
d[k++]=c[j++];
else
while(i<=m)
d[k++]=c[i++];
}
double closest(point X[],point Y[],point Z[],int l,int r)
{
if(r-l==1)return dis(X[l],X[r]);
if(r-l==2)
{
double d1=dis(X[l],X[r]);
double d2=dis(X[l+1],X[r]);
double d3=dis(X[l],X[l+1]);
if(d1<d2&&d1<d3)return d1;
if(d2<d3)return d2;
return d3;
}
int m=(l+r)/2;
int f=l,g=m+1;
int i,j,k;
double d1,d2,dm;
for(i=l;i<=r;i++)
if(Y[i].id>m)Z[g++]=Y[i];
else Z[f++]=Y[i];
d1=closest(X,Z,Y,l,m);
d2=closest(X,Z,Y,m+1,r);
dm=min(d1,d2);
merge(Z,Y,l,m,r);
k=l;
for(i=l;i<=r;i++)
if(fabs(X[m].x-Y[i].x)<dm)Z[k++]=Y[i];
for(i=l;i<k;i++)
{
for(j=i+1;j<k&&Z[j].y-Z[i].y<dm;j++)
{
double tmp=dis(Z[i],Z[j]);
if(tmp<dm)dm=tmp;
}
}
return dm;
}
int main()
{
int n,i;
while(scanf("%d",&n)&&n)
{
for(i=0;i<n;i++)
cin>>aa[i].x>>aa[i].y;
sort(aa,aa+n,cmp_x);
for(i=0;i<n;i++)
{
aa[i].id=i;
bb[i]=aa[i];
}
//memcpy(b,a,n*sizeof(a[0]));
sort(bb,bb+n,cmp_y);
printf("%.2lf\n",closest(aa,bb,cc,0,n-1)/2);
}
return 0;
}