算法竞赛入门经典训练指南－4.1学习笔记

//向量基本运算代码
struct Point
{
double x, y;
Point(double = 0, double y = 0):x(x), y(y){ }
};

typedef Point Vector;//从程序实现上，Vector只是Point的别名

//向量＋向量＝向量， 点＋向量＝点
Vector operator + (Vector A, Vector B){ return Vector(A.x + B.x, A.y + B.y); }

//向量-向量＝向量， 点-向量＝点
Vector operator - (Vector A, Vector B){ return Vector(A.x - B.x, A.y - B.y); }

//向量*数＝向量
Vector operator * (Vector A, double p){ return Vector(A.x*p, A.y*p);}

//向量/数＝向量
Vector operator * (Vector A, double p){ return Vector(A.x/p, A.y/p);}

bool operator < (const Point &a, const Point& b)
{
return a.x < b.x || (a.x == b.x && a.y < b.y);
}

const double eps 1e-10;
int dcmp(double x)
{
if(fabs(x) < eps)return 0;//fabs(x)x的浮点数绝对值
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;
}