杭电 HOJ 1588 Segment set 解题报告

#include <iostream>
using namespace std;

int root[1001];
int num[1001];

int find(int x)
{
return root[x]?(root[x]=find(root[x])):x;
}

void u(int x,int y)
{
int a=find(x);
int b=find(y);
if(a!=b)
num[root[b]=a]+=num[b];
}

struct p
{
double x1,y1,x2,y2;
} line[1001];

double area(double a,double b,double c,double d)
{
return (a*d-b*c);
};

bool across(p &a,p &b)
{
if(area(a.x2-a.x1,a.y2-a.y1,b.x1-a.x1,b.y1-a.y1)*area(a.x2-a.x1,a.y2-a.y1,b.x2-a.x1,b.y2-a.y1)<=0
&&
area(b.x2-b.x1,b.y2-b.y1,a.x1-b.x1,a.y1-b.y1)*area(b.x2-b.x1,b.y2-b.y1,a.x2-b.x1,a.y2-b.y1)<=0)
return true;
return false;
}

int main()
{
char s[2];
int cas,m,n,i,j,ans,t;
scanf("%d",&cas);
while(cas--)
{
m=1;
memset(root,0,sizeof(root));
memset(num,0,sizeof(num));

scanf("%d",&n);
for(int i=0;i<n;i++)
{
scanf("%s",s);
if(s[0]=='P')
{
scanf("%lf%lf%lf%lf",&line[m].x1,&line[m].y1,&line[m].x2,&line[m].y2);
root[m]=0;
num[m]=1;
for(j=1;j<m;j++)
if(across(line[j],line[m]))
u(m,j);
m++;
}
else
{
scanf("%d",&t);
printf("%d\n",num[find(t)]);
}
}
if(cas)
printf("\n");
}
}