给定两直线，判定相交，重合，或求出交点
验模板的题目
代码：
#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>using namespace std;int t;struct Point {double x, y;Point() {}Point(double x, double y) {this->x = x;this->y = y;}void read() {scanf("%lf%lf", &x, &y);}};typedef Point Vector;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 eps = 1e-8;int dcmp(double x) {if (fabs(x) < eps) return 0;else return x < 0 ? -1 : 1;}double Cross(Vector A, Vector B) {return A.x * B.y – A.y * B.x;} //叉积bool LineCoincide(Point p1, Point p2, Point p3) {return dcmp(Cross(p2 – p1, p3 – p1)) == 0;}bool LineParallel(Point P, Vector v, Point Q, Vector w) {return dcmp(v.x * w.y – v.y * w.x) == 0;}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;}int main() {scanf("%d", &t);printf("INTERSECTING LINES OUTPUT\n");while (t–) {Point p1, p2, p3, p4;p1.read(); p2.read();p3.read(); p4.read();if (LineCoincide(p1, p2, p3) && LineCoincide(p1, p2, p4))printf("LINE\n");else if (LineParallel(p1, p2 – p1, p3, p4 – p3))printf("NONE\n");else {Point ans = GetLineIntersection(p1, p2 – p1, p3, p4 – p3);printf("POINT %.2f %.2f\n", ans.x, ans.y);}}printf("END OF OUTPUT\n");return 0;}
，，再回头，便生出无限羁绊。那是彼此的刺在对方心里留下的痕迹，
