UVa 10902 Pick-up Sticks

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <vector>
using namespace std;
#define MAXN 100002
struct point {
double x,y;
point (double x = 0 ,double y = 0){
this->x = x;
this->y = y;
}
};
struct line{
point st,en;
line(point st,point en){
this->st = st;
this->en = en;
}
};
class Isolated{
private:
int segNum;
vector<line> segments;
int ans[MAXN];
int ansNum;
public:
void init();
void readData(int num);
void process();
bool isCross(line la,line lb);
bool isInSeg(point a,point la,point lb);//点是否在线段l上
long long dir(point i,point j,point k);//向量叉积
};
void Isolated::init(){
ansNum = 0;
segments.clear();
}
void Isolated::readData(int num){
segNum = num;
double x1,y1,x2,y2;
while(num--){
scanf("%lf %lf %lf %lf",&x1,&y1,&x2,&y2);
point st(x1,y1),en(x2,y2);
line la(st,en);
segments.push_back(la);
}
}
void Isolated::process(){
bool isColl;//线段是否是孤立的
for(int i = 0;i < segNum;i++){
isColl = true;
for(int j = segNum - 1;j >= 0;j--){
if(i==j)continue;
else{
if(isCross(segments[i],segments[j])){
if(i < j){//如果和之后落下的相交，那么就被排除
isColl = false;
}break;
}
}
}
if(isColl)
{
ans[ansNum++] = i + 1;
}
}
cout<<"Top sticks: ";
for(int k = 0; k < ansNum;k++){
if(k < ansNum - 1)
cout<<ans[k]<<", ";
else
cout<<ans[k]<<"."<<endl;
}
}
bool Isolated::isCross(line la,line lb){
long long dir1 = dir(la.st,la.en,lb.st);
long long dir2 = dir(la.st,la.en,lb.en);
long long dir3 = dir(lb.st,lb.en,la.st);
long long dir4 = dir(lb.st,lb.en,la.en);
if(dir1 * dir2 < 0 && dir3*dir4 < 0){// 线段 相交
return true;
}
else if(dir1 == 0&& isInSeg(la.st,la.en,lb.st)){//向量共线，判断是否重合
return true;
}
else if(dir2 == 0&&isInSeg(la.st,la.en,lb.en)){
return true;
}
else if(dir3 == 0&&isInSeg(lb.st,lb.en,la.st)){
return true;
}
else if(dir4 == 0&&isInSeg(lb.st,lb.en,la.en)){
return true;
//return false;
}
else
return false;
}
bool Isolated::isInSeg(point la,point lb,point a){
if((min(la.x,lb.x) <= a.x && a.x <= max(la.x,lb.x)) &&
(min(la.y,lb.y) <= a.y && a.y <= max(la.y,lb.y)))
return true;
else
return false;
}
long long Isolated::dir(point i,point j,point k){//向量叉积
return ((j.x - i.x)*(k.y - i.y)-(k.x - i.x)*(j.y - i.y));
}
int main()
{
#ifndef ONLINE_JUDGE
freopen("D:\\acm.txt","r",stdin);
#endif // ONLINE_JUDGE
int cases;

Isolated isolated;
while(cin>>cases,cases != 0){
isolated.init();
isolated.readData(cases);
isolated.process();
}
return 0;
}