hdu 1558 Segment set（并查集+判断线段是否相交）

代码：

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

int father[1005];
int son_cnt[1005];
char s[5];
//int cnt;

struct point
{
    double x,y;
};

point a[1005],b[1005];

int find_father(int x)
{
    int r=x;
    while(father[x]!=x)
    {
        x=father[x];
    }
    father[r]=x;
    //ans[x]++;
    return x;
}

double xmult(point a,point b,point c) //大于零代表a,b,c左转
{
    return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
}
bool OnSegment(point a,point b,point c) 		//a,b,c共线时有效
{
    return c.x>=min(a.x,b.x)&&c.x<=max(a.x,b.x)&&c.y>=min(a.y,b.y)&&c.y<=max(a.y,b.y);
}

bool Cross(point a,point b,point c,point d) //判断ab 与cd是否相交
{
    double d1,d2,d3,d4;
    d1=xmult(c,d,a);
    d2=xmult(c,d,b);
    d3=xmult(a,b,c);
    d4=xmult(a,b,d);
    if(d1*d2<0&&d3*d4<0)	return 1;
    else	if(d1==0&&OnSegment(c,d,a))	return 1;
    else	if(d2==0&&OnSegment(c,d,b))	return 1;
    else	if(d3==0&&OnSegment(a,b,c))	return 1;
    else	if(d4==0&&OnSegment(a,b,d))	return 1;
    return 0;
}
void mergee(int x,int y)
{
    //if(intersect3(a[x],b[x],a[y],b[y]))
    //{
        x=find_father(x);
        y=find_father(y);
        if(x!=y)
        {
            father[y]=x;
            son_cnt[x]+=son_cnt[y];
            //son_cnt[y]=son_cnt[x];
           // son_cnt[y]--;
        }
    //}
}

int main()
{
    int t;
    int cnt;
    scanf("%d",&t);
    while(t--)
    {
        //memset(ans,0,sizeof(ans));
        int n;
        scanf("%d",&n);
        for(int i=1; i<=n; i++)
        {
            father[i]=i;
            son_cnt[i]=1;
        }
        cnt=0;
        for(int i=1;i<=n;i++)
        {
            scanf("%s",s);
            if(strcmp(s,"P")==0)
            {
                cnt++;
                scanf("%lf%lf%lf%lf",&a[cnt].x,&a[cnt].y,&b[cnt].x,&b[cnt].y);
                for(int j=1;j<cnt;j++)
                {
                    if(Cross(a[j],b[j],a[cnt],b[cnt]))
                        mergee(j,cnt);
                }
            }
            else
            {
                int ttt;
                scanf("%d",&ttt);
                printf("%d\n",son_cnt[find_father(ttt)]);
            }
        }
        if(t)
            printf("\n");
    }
    return 0;
}