hdu 1147线段判断相交问题

pc代码

hdu 1147
#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<queue>
using namespace std;
const int N=1002;
const double eps=0.0000000001;//注意设置一个精度

struct node
{
    double ux,uy;
    double lx,ly;
    int num;
    bool tab;
};
queue<node> ss;

double jud1(node a,int x,int y)
{
    return (a.ux-a.lx)*(y-a.ly)-(a.uy-a.ly)*(x-a.lx);
}
bool jud2(node a,int x,int y)
{
    if(a.ux==x&&a.uy==y)return true;
    if(a.lx==x&&a.ly==y)return true;
    return false;
}
bool judtoach(node a,node b)
{
    double k1=jud1(a,b.lx,b.ly);
    double k2=jud1(a,b.ux,b.uy);
    double k3=jud1(b,a.lx,a.ly);
    double k4=jud1(b,a.ux,a.uy);
    if(k1*k2<-eps&&k3*k4<-eps)return true;
    if(k1<eps&&k1>-eps&&jud2(a,b.lx,b.ly))return true;
    if(k2<eps&&k2>-eps&&jud2(a,b.ux,b.uy))return true;
    if(k3<eps&&k3>-eps&&jud2(b,a.lx,a.ly))return true;
    if(k4<eps&&k4>-eps&&jud2(b,a.ux,a.uy))return true;
    return false;
}

int main()
{
    int n;
    node a,b;
    while(scanf("%d",&n),n)
    {
        while(!ss.empty())ss.pop();
        for(int i=0;i<n;i++)
        {
            scanf("%lf%lf%lf%lf",&a.ux,&a.uy,&a.lx,&a.ly);
            a.tab=true;//用tab标记队列队尾，到队尾时及时跳出循环
            a.num=i+1;
            ss.push(a);//用一个队列存储所有没有被覆盖的木棒
            b=ss.front();
            ss.pop();
            while(!b.tab)
            {
                if(judtoach(b,a))//如果这个新加入的木棒与之前一个木棒有交点，把原来的那个木棒去掉
                {
                    b=ss.front();
                    ss.pop();
                    continue;
                }
                ss.push(b);
                b=ss.front();
                ss.pop();
            }
            b.tab=false;
            ss.push(b);
        }
        cout<<"Top sticks:";
        while(1)
        {
            a=ss.front();
            cout<<" "<<a.num;
            ss.pop();
            if(ss.empty()){cout<<"."<<endl;break;}
            else cout<<",";
        }
    }
    return 0;
}

代码

#include <iostream>
#include <stdio.h>

using namespace std;

typedef struct node
{
    double x;
    double y;
}point;
typedef struct ed
{
    point a;
    point b;
    int is_top;
}edge;
edge e[100005];

point make_e(point x,point y)
{
    point a;
    a.x = x.x - y.x;
    a.y = x.y - y.y;
    return a;
}

double cha(point x,point y)
{
    return x.x*y.y - y.x*x.y;
}
double dian(point x,point y)
{
    return x.x*y.x + y.y*x.y;
}
double cross(edge a,point c)
{
    point e1,e2;
    e1 = make_e(a.a,c);
    e2 = make_e(a.a,a.b);
    return cha(e2,e1);
}

int main()
{
    int n,i,j;
    while(scanf("%d",&n)&&n)
    {
        for(i = 0;i < n;i++)
        scanf("%lf %lf %lf %lf",&e[i].a.x,&e[i].a.y,&e[i].b.x,&e[i].b.y),e[i].is_top = 0;
        int count = n;
        for(i = 0;i < n;i++)
        {
            for(j = i+1;j < n;j++)
            {
                if(cross(e[i],e[j].a)*cross(e[i],e[j].b) < 0 && cross(e[j],e[i].a)*cross(e[j],e[i].b) < 0)
                {
                    e[i].is_top = 1;
                    count--;
                    break;
                }

            }
        }
        printf("Top sticks: ");
        count--;
        for(i = 0;i < n;i++)
        {
            if(e[i].is_top == 0){

                printf("%d",i+1);
                if(count)
                printf(", "),count--;
                else
                printf(".\n");
            }
        }
    }
    return 0;
}