UVa 10902 Pick-up Sticks

#include <iostream>#include <cstdio>#include <cstring>#include <cstdlib>#include <vector>using namespace std;#define MAXN 100002struct 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;}