计算几何-526互联

快考NOIP了我在这怼计算几何属于是脑子有点问题，随手记一下板子啥的得了，到时候有啥题目慢慢选上来

基础东西

向量类

(叉积用/只是习惯，懒得写cross了)

 1 struct point {
 2     double x,y;
 3     friend point operator - (const point &p1, const point &p2) {
 4         return (point) {p1.x - p2.x, p1.y - p2.y};
 5     }
 6     friend point operator + (const point &p1, const point &p2) {
 7         return (point) {p1.x + p2.x, p1.y + p2.y};
 8     }
 9     friend double operator * (const point &p1, const point &p2 {
10         return p1.x * p2.x + p1.y * p2.y;
11     }
12     friend double operator / (const point &p1, const point &p2) {// 叉积
13         return p1.x * p2.y - p2.x * p1.y; 
14     }
15 }

判断点与直线的关系