POJ 2653 Pick-up sticks

从此踏上计算几何的不归路……

#include <algorithm>
#include <iostream>
#include <fstream>
#include <sstream>
#include <iomanip>

#include <map>
#include <set>
#include <list>
#include <stack>
#include <queue>
#include <deque>
#include <vector>
#include <string>
#include <bitset>
#include <memory>
#include <complex>
#include <numeric>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <time.h>
#include <ctype.h>
#include <locale.h>

using namespace std;

#pragma pack(4)

const double  eps = 1e-8;
const double   pi = acos(-1.0);
const int     inf = 0x7f7f7f7f;

#define loop(a,n)                            \
    for(int i=0;n>i;i++)                     \
        cout<<a[i]<<(i!=n-1?' ':'\n')
#define loop2(a,n,m)                         \
    for(int i=0;n>i;i++)                     \
        for(int j=0;m>j;j++)                 \
            cout<<a[i][j]<<(j!=m-1?' ':'\n')

#define   at(a,i) ((a)&(1<<(i)))
#define   nt(a,i) ((a)^(1<<(i)))
#define set1(a,i) ((a)|(1<<(i)))
#define set0(a,i) ((a)&(~(1<<(i))))

#define gret(a,b) (((a)-(b))>eps)
#define less(a,b) (((b)-(a))>eps)
#define greq(a,b) (((a)-(b))>-eps)
#define leeq(a,b) (((b)-(a))>-eps)
#define equl(a,b) (fabs((a)-(b))<eps)

#define lmax(a,b) ((a)>(b)?(a):(b))
#define lmin(a,b) ((a)<(b)?(a):(b))
#define fmax(a,b) (gret(a,b)?(a):(b))
#define fmin(a,b) (less(a,b)?(a):(b))

const int MAXV = 100002;

struct point
{
    double c[2];
    point(double x=0,double y=0)
    {
        c[0]=x;
        c[1]=y;
    }
    double & operator [] (int i)
    {
        return c[i];
    }
    point operator + (point argu)
    {
        return point(c[0]+argu[0],c[1]+argu[1]);
    }
    point operator - (point argu)
    {
        return point(c[0]-argu[0],c[1]-argu[1]);
    }
    double operator * (point argu)
    {
        return c[0]*argu[0]+c[1]*argu[1];
    }
    double operator / (point argu)
    {
        return c[0]*argu[1]-c[1]*argu[0];
    }
};
double area2(point o,point a,point b)
{
    return (a-o)/(b-o);
}
struct seg
{
    point p[2];
    seg(point a,point b)
    {
        p[0]=a;
        p[1]=b;
    }
    seg(double x1=0,double y1=0,double x2=0,double y2=0)
    {
        p[0]=point(x1,y1);
        p[1]=point(x2,y2);
    }
    point & operator [] (int i)
    {
        return p[i];
    }
}a[MAXV];
bool inter(seg a,seg b)
{
    return
        less(area2(a[0],a[1],b[0])*area2(a[0],a[1],b[1]),0)&&
        less(area2(b[0],b[1],a[0])*area2(b[0],b[1],a[1]),0);
}

int n;

int main()
{
    #ifndef ONLINE_JUDGE
    freopen("Pick-up sticks.txt","r",stdin);
    #endif

    while(scanf("%d",&n),n)
    {
        for(int i=1;n>=i;i++)
        {
            scanf("%lf %lf %lf %lf",&a[i][0][0],&a[i][0][1],&a[i][1][0],&a[i][1][1]);
        }
        printf("Top sticks:");
        int cnt=0;
        for(int i=1;n>=i;i++)
        {
            bool flag=true;
            for(int j=i+1;n>=j;j++)
            {
                if(inter(a[i],a[j]))
                {
                    flag=false;
                    break;
                }
            }
            if(flag)
            {
                if(cnt++) printf(",");
                printf(" %d",i);
            }
        }
        printf(".\n");
    }
    return 0;
}

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