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  • LA 2797

    题目链接

    题意:训练指南283页;

    #include <iostream>
    #include <cstdio>
    #include <cstring>
    #include <cstdlib>
    #include <cmath>
    #include <vector>
    #include <queue>
    #include <map>
    #include <algorithm>
    #include <set>
    #define MM(a) memset(a,0,sizeof(a))
    typedef long long ll;
    typedef unsigned long long ULL;
    const double eps = 1e-14;
    const int inf = 0x3f3f3f3f;
    const double pi=acos(-1);
    using namespace std;
    
    struct Point {
        double x, y;
        double ang;
        Point() {}
        Point(double x,double y) {
            this->x = x;
            this->y = y;
        }
        void read() {
            scanf("%lf %lf", &x, &y);
        }
        bool operator <(const Point w) const
        {
            if(this->x==w.x)  return this->y<w.y;
            else   return this->x<w.x;
        }
    };
    typedef Point Vector;
    /*
    struct Line{
        Point a;
        Point v,nor;
        double ang;
        Line(){};
        Line(Point u,Vector w):a(u),v(w){};
        bool operator <(const Line q) const{
           return this->ang<q.ang;
        }
    };
    
    struct Circle {
        Point c;
        double r;
        Circle(){};
        Circle(Point c, double r) {
            this->c = c;
            this->r = r;
        }
        Point point(double a) {
            return Point(c.x + cos(a) * r, c.y + sin(a) * r);
        }
    
    };
    */
    Vector operator + (Vector A, Vector B) {
        return Vector(A.x + B.x, A.y + B.y);
    }
    
    Vector operator - (Vector A, Vector B) {
        return Vector(A.x - B.x, A.y - B.y);
    }
    
    Vector operator * (Vector A, double p) {
        return Vector(A.x * p, A.y * p);
    }
    
    Vector operator / (Vector A, double p) {
        return Vector(A.x / p, A.y / p);
    }
    
    const double PI = acos(-1.0);
    
    int dcmp(double  x) {
        if (fabs(x) < eps) return 0;
        else return x < 0 ? -1 : 1;
    }
    
    bool operator == (const Point& a, const Point& b) {
        return dcmp(a.x - b.x) == 0 && dcmp(a.y - b.y) == 0;
    }
    
    bool operator < (const Point& a, const Point& b) {
        return a.x < b.x || (a.x == b.x && a.y < b.y);
    }
    
    double torad(double ang)
    {
        return ang/180*pi;
    }
    
    double Dot(Vector A, Vector B) {return A.x * B.x + A.y * B.y;} //点积
    double Length(Vector A) {return sqrt(Dot(A, A));} //向量的模
    double Angle(Vector A, Vector B) {return acos(Dot(A, B) / Length(A) / Length(B));} //向量夹角
    double Cross(Vector A, Vector B) {return A.x * B.y - A.y * B.x;} //叉积
    double Area2(Point A, Point B, Point C) {return Cross(B - A, C - A);} //有向面积
    double angle(Vector v) {return atan2(v.y, v.x);}
    
    Point GetLineIntersection(Point P, Vector v, Point Q, Vector w) {
        Vector u = P - Q;
        double t = Cross(w, u) / Cross(v, w);
        return P + v * t;
    }
    
    Vector Rotate(Vector A, double rad) {
        return Vector(A.x * cos(rad) - A.y * sin(rad), A.x * sin(rad) + A.y * cos(rad));
    }
    
    double DistanceToLine(Point P, Point A, Point B) {
        Vector v1 = B - A, v2 = P - A;
        return fabs(Cross(v1, v2)) / Length(v1);
    }
    
    //线段的规范相交
    bool SegmentProperIntersection(Point a1, Point a2, Point b1, Point b2) {
        double c1 = Cross(a2 - a1, b1 - a1), c2 = Cross(a2 - a1, b2 - a1),
                c3 = Cross(b2 - b1, a1 - b1), c4 = Cross(b2 - b1, a2 - b1);
        return dcmp(c1) * dcmp(c2) < 0 && dcmp(c3) * dcmp(c4) < 0;
    }
    
    //点在线段上(不含端点)
    bool OnSegment(Point p, Point a1, Point a2) {
        return dcmp(Cross(a1 - p, a2 - p)) == 0 && dcmp(Dot(a1 - p, a2 - p))<0;
    }
    
    //线段不规范相交 (自己写的)
    bool SegmentinProperIntersection(Point a1, Point a2, Point b1, Point b2)
    {
        if(SegmentProperIntersection(a1, a2, b1,b2))
           return 1;
        if(OnSegment(b1, a1, a2))
           return 1;
        if(OnSegment(b2, a1, a2))
           return 1;
        return 0;
    }
    
    Point p[1005];
    Vector v[105];
    int n,num,f[505][505],vis[505];
    vector<Point> q;
    
    bool Onanysegment(Point w)
    {
       for(int i=0;i<n;i++)
            if(OnSegment(w,p[i],p[i+n]))
                return true;
       return false;
    }
    
    bool Intercetwithangsegment(Point a,Point b)
    {
        for(int i=0;i<n;i++)
            if(SegmentProperIntersection(a,b,p[i],p[i+n]))
                 return true;
        return false;
    }
    
    void init()
    {
       memset(f,0,sizeof(f));
       memset(vis,0,sizeof(vis));
       q.clear();
    
       p[2*n]=Point(0,0);p[2*n+1]=Point(1000,1000);
       q.push_back(p[2*n]);q.push_back(p[2*n+1]);
    
       for(int i=0;i<=2*n-1;i++)
         if(!Onanysegment(p[i]))
           q.push_back(p[i]);//对于处在线段中间的点,不进入构图,否则会错,想像一下,两条线段共端点且共线
    
       num=q.size();
       for(int i=0;i<num;i++)
         for(int j=i+1;j<num;j++)
              if(!Intercetwithangsegment(q[i],q[j]))
                f[j][i]=f[i][j]=1;//说明这两个点可以直接到达
    
       //for(int i=0;i<num;i++)
         // for(int j=0;j<num;j++)
           //cout<<i<<" "<<j<<" "<<f[i][j]<<endl;
    }
    
    bool dfs(int cur)
    {
       // printf("cur:%d
    ",cur);
        if(cur==1) return true;
        vis[cur]=1;
        for(int i=0;i<num;i++)
           if(!vis[i]&&f[cur][i]&&dfs(i))//dfs的标准格式
              return true;
        return false;
    }
    
    void solve()
    {
        if(dfs(0)) printf("no
    ");
        else printf("yes
    ");
    }
    
    int main()
    {
        while(~scanf("%d",&n)&&n)
        {
           for(int i=0;i<n;i++)
                {
                    p[i].read();p[i+n].read();
                    v[i]=(p[i+n]-p[i])/(Length(p[i+n]-p[i]));
                    p[i]=p[i]-v[i]*1e-5;
                    p[i+n]=p[i+n]+v[i]*1e-5;//进行端点的微小扰动
                }
           init();
           solve();
        }
        return 0;
    }
    

    wa代码:

    #include <iostream>
    #include <cstdio>
    #include <cstring>
    #include <cstdlib>
    #include <cmath>
    #include <vector>
    #include <queue>
    #include <map>
    #include <algorithm>
    #include <set>
    #define MM(a) memset(a,0,sizeof(a))
    typedef long long ll;
    typedef unsigned long long ULL;
    const double eps = 1e-14;
    const int inf = 0x3f3f3f3f;
    const double pi=acos(-1);
    using namespace std;
    
    struct Point {
        int x, y;
        double ang;
        Point() {}
        Point(int x,int y) {
            this->x = x;
            this->y = y;
        }
        void read() {
            scanf("%lf%lf", &x, &y);
        }
        bool operator <(const Point w) const
        {
            if(this->x==w.x)  return this->y<w.y;
            else   return this->x<w.x;
        }
    };
    typedef Point Vector;
    /*
    struct Line{
        Point a;
        Point v,nor;
        double ang;
        Line(){};
        Line(Point u,Vector w):a(u),v(w){};
        bool operator <(const Line q) const{
           return this->ang<q.ang;
        }
    };
    
    struct Circle {
        Point c;
        double r;
        Circle(){};
        Circle(Point c, double r) {
            this->c = c;
            this->r = r;
        }
        Point point(double a) {
            return Point(c.x + cos(a) * r, c.y + sin(a) * r);
        }
    
    };
    */
    Vector operator + (Vector A, Vector B) {
        return Vector(A.x + B.x, A.y + B.y);
    }
    
    Vector operator - (Vector A, Vector B) {
        return Vector(A.x - B.x, A.y - B.y);
    }
    
    Vector operator * (Vector A, double p) {
        return Vector(A.x * p, A.y * p);
    }
    
    Vector operator / (Vector A, double p) {
        return Vector(A.x / p, A.y / p);
    }
    
    const double PI = acos(-1.0);
    
    int dcmp(int x) {
        if (fabs(x) < eps) return 0;
        else return x < 0 ? -1 : 1;
    }
    
    bool operator == (const Point& a, const Point& b) {
        return dcmp(a.x - b.x) == 0 && dcmp(a.y - b.y) == 0;
    }
    
    bool operator < (const Point& a, const Point& b) {
        return a.x < b.x || (a.x == b.x && a.y < b.y);
    }
    
    double torad(double ang)
    {
        return ang/180*pi;
    }
    
    double Dot(Vector A, Vector B) {return A.x * B.x + A.y * B.y;} //点积
    double Length(Vector A) {return sqrt(Dot(A, A));} //向量的模
    double Angle(Vector A, Vector B) {return acos(Dot(A, B) / Length(A) / Length(B));} //向量夹角
    double Cross(Vector A, Vector B) {return A.x * B.y - A.y * B.x;} //叉积
    double Area2(Point A, Point B, Point C) {return Cross(B - A, C - A);} //有向面积
    double angle(Vector v) {return atan2(v.y, v.x);}
    
    Point GetLineIntersection(Point P, Vector v, Point Q, Vector w) {
        Vector u = P - Q;
        double t = Cross(w, u) / Cross(v, w);
        return P + v * t;
    }
    
    Vector Rotate(Vector A, double rad) {
        return Vector(A.x * cos(rad) - A.y * sin(rad), A.x * sin(rad) + A.y * cos(rad));
    }
    
    double DistanceToLine(Point P, Point A, Point B) {
        Vector v1 = B - A, v2 = P - A;
        return fabs(Cross(v1, v2)) / Length(v1);
    }
    
    //线段的规范相交
    bool SegmentProperIntersection(Point a1, Point a2, Point b1, Point b2) {
        int c1 = Cross(a2 - a1, b1 - a1), c2 = Cross(a2 - a1, b2 - a1),
                c3 = Cross(b2 - b1, a1 - b1), c4 = Cross(b2 - b1, a2 - b1);
        return dcmp(c1) * dcmp(c2) < 0 && dcmp(c3) * dcmp(c4) < 0;
    }
    
    //点在线段上(含端点)
    bool OnSegment(Point p, Point a1, Point a2) {
        return dcmp(Cross(a1 - p, a2 - p)) == 0 && dcmp(Dot(a1 - p, a2 - p))<=0;
    }
    
    //线段不规范相交 (自己写的)
    bool SegmentinProperIntersection(Point a1, Point a2, Point b1, Point b2)
    {
        if(SegmentProperIntersection(a1, a2, b1,b2))
           return 1;
        if(OnSegment(b1, a1, a2))
           return 1;
        if(OnSegment(b2, a1, a2))
           return 1;
        return 0;
    }
    /*
    Vector AngleBisector(Point p, Vector v1, Vector v2){//给定两个向量,求角平分线
        double rad = Angle(v1, v2);
        return Rotate(v1, dcmp(Cross(v1, v2)) * 0.5 * rad);
    }
    
    //求线与x轴的真实角(0<=X<180)
    double RealAngleWithX(Vector a){
        Vector b(1, 0);
        if (dcmp(Cross(a, b)) == 0) return 0.0;
        else if (dcmp(Dot(a, b) == 0)) return 90.0;
        double rad = Angle(a, b);
        rad = (rad / PI) * 180.0;
        if (dcmp(a.y) < 0) rad = 180.0 - rad;
        return rad;
    }
    
    //求直线与圆的交点
    int getLineCircleIntersection(Point p, Vector v, Circle c, vector<Point> &sol) {
        double a1 = v.x, b1 = p.x - c.c.x, c1 = v.y, d1 = p.y - c.c.y;
        double e1 = a1 * a1 +  c1 * c1, f1 = 2 * (a1 * b1 + c1 * d1), g1 = b1 * b1 + d1 * d1 - c.r * c.r;
        double delta = f1 * f1 - 4 * e1 * g1, t;
        if(dcmp(delta) < 0) return 0;
        else if(dcmp(delta) == 0){
            t = (-f1) / (2 * e1);
            sol.push_back(p + v * t);
            return 1;
        } else{
            t = (-f1 + sqrt(delta)) / (2 * e1); sol.push_back(p + v * t);
            t = (-f1 - sqrt(delta)) / (2 * e1); sol.push_back(p + v * t);
            return 2;
        }
    }
    
    //两圆相交
    int getCircleCircleIntersection(Circle C1, Circle C2, vector<Point> &sol) {
        double d = Length(C1.c - C2.c);
        if (dcmp(d) == 0) {
            if (dcmp(C1.r - C2.r) == 0) return -1; // 重合
            return 0;
        }
        if (dcmp(C1.r + C2.r - d) < 0) return 0;
        if (dcmp(fabs(C1.r - C2.r) - d) > 0) return 0;
        double a = angle(C2.c - C1.c);
        double da = acos((C1.r * C1.r + d * d - C2.r * C2.r) / (2 * C1.r * d));
        Point p1 = C1.point(a - da), p2 = C1.point(a + da);
        sol.push_back(p1);
        if(p1 == p2) return 1;
        sol.push_back(p2);
        return 2;
    
    }
    
    //点到圆的切线
    int getTangents(Point p, Circle C, Vector *v) {
        Vector u = C.c - p;
        double dist = Length(u);
        if (dist < C.r) return 0;
        else if (dcmp(dist - C.r) == 0) {
            v[0] = Rotate(u, PI / 2);
            return 1;
        } else {
            double ang = asin(C.r / dist);
            v[0] = Rotate(u, -ang);
            v[1] = Rotate(u, +ang);
            return 2;
        }
    }
    
    //两圆公切线
    //a[i], b[i]分别是第i条切线在圆A和圆B上的切点
    int getCircleTangents(Circle A, Circle B, Point *a, Point *b) {
        int cnt = 0;
        if (A.r < B.r) { swap(A, B); swap(a, b); }
        //圆心距的平方
        double d2 = (A.c.x - B.c.x) * (A.c.x - B.c.x) + (A.c.y - B.c.y) * (A.c.y - B.c.y);
        double rdiff = A.r - B.r;
        double rsum = A.r + B.r;
        double base = angle(B.c - A.c);
        //重合有无限多条
        if (d2 == 0 && dcmp(A.r - B.r) == 0) return -1;
        //内切
        if (dcmp(d2 - rdiff * rdiff) == 0) {
            a[cnt] = A.point(base);
            b[cnt] = B.point(base);
            cnt++;
            return 1;
        }
        //有外公切线
        double ang = acos((A.r - B.r) / sqrt(d2));
        a[cnt] = A.point(base + ang); b[cnt] = B.point(base + ang); cnt++;
        a[cnt] = A.point(base - ang); b[cnt] = B.point(base - ang); cnt++;
    
        //一条内切线,两条内切线
        if (dcmp(d2 - rsum*rsum) == 0) {
            a[cnt] = A.point(base); b[cnt] = B.point(PI + base); cnt++;
        } else if (dcmp(d2 - rsum*rsum) > 0) {
            double ang = acos((A.r + B.r) / sqrt(d2));
            a[cnt] = A.point(base + ang); b[cnt] = B.point(base + ang); cnt++;
            a[cnt] = A.point(base - ang); b[cnt] = B.point(base - ang); cnt++;
        }
        return cnt;
    }
    
    //三角形外切圆
    Circle CircumscribedCircle(Point p1, Point p2, Point p3) {
        double Bx = p2.x - p1.x, By = p2.y - p1.y;
        double Cx = p3.x - p1.x, Cy = p3.y - p1.y;
        double D = 2 * (Bx * Cy - By * Cx);
        double cx = (Cy * (Bx * Bx + By * By) - By * (Cx * Cx + Cy * Cy)) / D + p1.x;
        double cy = (Bx * (Cx * Cx + Cy * Cy) - Cx * (Bx * Bx + By * By)) / D + p1.y;
        Point p = Point(cx, cy);
        return Circle(p, Length(p1 - p));
    }
    
    //三角形内切圆
    Circle InscribedCircle(Point p1, Point p2, Point p3) {
        double a = Length(p2 - p3);
        double b = Length(p3 - p1);
        double c = Length(p1 - p2);
        Point p = (p1 * a + p2 * b + p3 * c) / (a + b + c);
        return Circle(p, DistanceToLine(p, p1, p2));
    }
    
    //求经过点p1,与直线(p2, w)相切,半径为r的一组圆
    int CircleThroughAPointAndTangentToALineWithRadius(Point p1, Point p2, Vector w, double r, vector<Point> &sol) {
        Circle c1 = Circle(p1, r);
        double t = r / Length(w);
        Vector u = Vector(-w.y, w.x);
        Point p4 = p2 + u * t;
        int tot = getLineCircleIntersection(p4, w, c1, sol);
        u = Vector(w.y, -w.x);
        p4 = p2 + u * t;
        tot += getLineCircleIntersection(p4, w, c1, sol);
        return tot;
    }
    
    //给定两个向量,求两向量方向内夹着的圆的圆心。圆与两线均相切,圆的半径已给定
    Point Centre_CircleTangentTwoNonParallelLineWithRadius(Point p1, Vector v1, Point p2, Vector v2, double r){
        Point p0 = GetLineIntersection(p1, v1, p2, v2);
        Vector u = AngleBisector(p0, v1, v2);
        double rad = 0.5 * Angle(v1, v2);
        double l = r / sin(rad);
        double t = l / Length(u);
        return p0 + u * t;
    }
    
    //求与两条不平行的直线都相切的4个圆,圆的半径已给定
    int CircleThroughAPointAndTangentALineWithRadius(Point p1, Vector v1, Point p2, Vector v2, double r, Point *sol) {
        int ans = 0;
        sol[ans++] = Centre_CircleTangentTwoNonParallelLineWithRadius(p1, v1, p2, v2, r);
        sol[ans++] = Centre_CircleTangentTwoNonParallelLineWithRadius(p1, v1 * -1, p2, v2, r);
        sol[ans++] = Centre_CircleTangentTwoNonParallelLineWithRadius(p1, v1, p2, v2 * -1, r);
        sol[ans++] = Centre_CircleTangentTwoNonParallelLineWithRadius(p1, v1 * -1, p2, v2 * -1, r);
        return ans;
    }
    
    //求与两个相离的圆均外切的一组圆,三种情况
    int CircleTangentToTwoDisjointCirclesWithRadius(Circle c1, Circle c2, double r, Point *sol){
        double dis1 = c1.r + r + r + c2.r;
        double dis2= Length(c1.c - c2.c);
        if(dcmp(dis1 - dis2) < 0) return 0;
        Vector u = c2.c - c1.c;
        double t = (r + c1.r) / Length(u);
        if(dcmp(dis1 - dis2)==0){
            Point p0 = c1.c + u * t;
            sol[0] = p0;
            return 1;
        }
        double aa = Length(c1.c - c2.c);
        double bb = r + c1.r, cc = r + c2.r;
        double rad = acos((aa * aa + bb * bb - cc * cc) / (2 * aa * bb));
        Vector w = Rotate(u, rad);
        Point p0 = c1.c + w * t;
        sol[0] = p0;
        w = Rotate(u, -rad);
        p0 = c1.c + w * t;
        sol[1] = p0;
        return 2;
    }
    //判断点与圆的位置关系(自己写的)
    int  pointincircle(Point a,Circle o)
    {
         double l=Length(o.c-a);
         if(dcmp(l-o.r)>0)
               return 1;
         else if(dcmp(l-o.r)==0)
               return 0;
         else if(dcmp(l-o.r)<0)
               return -1;
    }
    int ConvexHull(Point *p, int n, Point* ch)         //求凸包
     {
         sort(p, p + n);//先按照x,再按照y
         int m = 0;
         for(int i = 0; i < n; i++)
         {
             while(m > 1 && Cross(ch[m-1] - ch[m-2], p[i] - ch[m-2]) <= 0) m--;
            ch[m++] = p[i];
        }
        int k = m;
         for(int i = n-2; i >= 0; i--)
        {
              while(m > k && Cross(ch[m-1] - ch[m-2], p[i] - ch[m-2]) <= 0) m--;
              ch[m++] = p[i];
          }
          if(n > 1) m--;
          return m;
    }
    
    double Polygonarea(Point *p,int n)
    {
       double area=0;
       for(int i=1;i<n-1;i++)
            area+=Cross(p[i]-p[0],p[i+1]-p[0]);
       return area/2;
    }
    
    //判断点是否在凸多边形内,注意是凸多变形,不是多边形
    int Pointinpolygon(Point p,Point *q,int m)
    {
        for(int i=0;i<m;i++)
           if(Cross(q[i+1]-q[i],p-q[i])<=0)
              return 0;
        return 1;
    }
    
    Point ne[105],tubao[105];
    
    void rotating_calipers(Point *p,int k)
    {
        double ans=0;
        p[k]=p[0];
        int q=1,temp;
        for(int i=0;i<k;i++)
        {
            while(temp=Cross(p[i+1]-p[i],p[q+1]-p[q])>0)  q=(q+1)%k;
            ans=max(Length(tubao[q]-tubao[i]),ans);
            if(!temp) ans=max(ans,Length(tubao[q+1]-tubao[i]));
        }
        printf("%d
    ",(int)(ans*ans+0.5));
    }
    */
    Point p[1005];
    Vector v[105];
    int n,f[505][505],vis[505];
    ;
    void init()
    {
       for(int i=0;i<n;i++)
          {
              p[i]=p[i]-v[i]*1e-5;
              p[i+n]=p[i+n]+v[i]*1e-5;
          }
       memset(f,0,sizeof(f));
       memset(vis,0,sizeof(vis));
       p[2*n]=Point(0,0);p[2*n+1]=Point(100,100);
       cout<<":7"<<endl;
       for(int i=0;i<=2*n+1;i++)
       for(int j=i+1;j<=2*n+1;j++)
       {
           int flag=1;
           cout<<":9"<<endl;
           for(int k=0;k<n;j++)
              if(SegmentProperIntersection(p[i],p[j],p[k],p[k+n]))
                   {cout<<13<<endl;flag=0;break;}
           cout<<":10"<<endl;
           if(flag) f[i][j]=f[j][i]=1;
           cout<<":8"<<endl;
       }
       cout<<":9"<<endl;
    }
    
    int dfs(int cur)
    {
        if(!vis[cur]) vis[cur]=1;
        else return 0;
        for(int i=0;i<=2*n+1;i++)
           if(!vis[i]&&f[cur][i]&&i!=cur)
                {
                    if(i==2*n+1) return 1;
                    else if(dfs(i)) return 1;
                    cout<<":3"<<endl;
                }
        cout<<":4"<<endl;
        return 0;
    }
    
    void solve()
    {
        if(dfs(2*n)) printf("yes
    ");
        else printf("no
    ");
    }
    
    int main()
    {
        while(~scanf("%d",&n)&&n)
        {
           for(int i=0;i<n;i++)
                {
                    scanf("%d %d",&p[i].x,&p[i].y);
                    scanf("%d %d",&p[i+n].x,&p[i+n].y);
                    v[i]=(p[i+n]-p[i])/(Length(p[i+n]-p[i]));
                }
           cout<<":1"<<endl;
           init();
           cout<<":2"<<endl;
           solve();
        }
        return 0;
    }
    


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  • 原文地址:https://www.cnblogs.com/smilesundream/p/6642531.html
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