POJ 1269 Intersecting Lines(简单计算几何，判断直线的关系）

#include <iostream>#include <cstring>#include <cstdlib>#include <cstdio>#include <cmath>#include <vector>#include <queue>#include <stack>#include <map>#include <set>#define LL long long using namespace std;struct Point{double x, y;Point(double x = 0, double y = 0) : x(x), y(y) { }};typedef Point Vector;Vector operator + (Vector A, Vector B) { return Vector(A.x + B.x, A.y + B.y); }Vector operator - (Point A, Point 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); }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;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;}double Cross(Vector A, Vector B) { return A.x * B.y - A.y * B.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;}int main(){int T;scanf("%d", &T);printf("INTERSECTING LINES OUTPUT\n");while(T--){Point p1, p2, p3, p4;scanf("%lf%lf%lf%lf%lf%lf%lf%lf", &p1.x, &p1.y, &p2.x, &p2.y, &p3.x, &p3.y, &p4.x, &p4.y);Vector A = p1 - p3; Vector B = p2 - p3;Vector C = p1 - p4; Vector D = p2 - p4;Vector F1 = p1 - p2; Vector F2 = p3 - p4;if(Cross(A, B) == 0 && Cross(C, D) == 0){printf("LINE\n");}else if(Cross(F1, F2) == 0){printf("NONE\n");}else{Point r = GetLineIntersection(p1, F1, p3, F2);printf("POINT %.2lf %.2lf\n", r.x, r.y);}}printf("END OF OUTPUT\n");return 0;}