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HDOJ 1007

HDOJ1007 Quoit Design

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#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(){

freopen("/Users/RichardLu/Code/C++/Algorithm/largeNumberSort/largeNumberSort/largeNumberSort/testcase.in", "r", stdin);
freopen("/Users/RichardLu/Code/C++/Algorithm/largeNumberSort/largeNumberSort/largeNumberSort/testcase.out", "w", stdout);

while(true)
{
scanf("%d",&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);
}
fclose(stdin);
fclose(stdout);

return 0;
}