2016-11-0921:00:46

判断点p0是否在线段p1p2上

1.先判断p0,p1,p2三点共线

2.在判断点p0在以p1p2为对角线的矩形内。

#include 
     
      #include 
      
       using namespace std;const double inf = 1e-10;struct point {    double x, y;};struct v {    point start, end;};bool onSegment(point p1, point p2, point p0) {    if (fabs((p1.x - p2.x)*(p1.y - p0.y) - (p1.x - p0.x)*(p1.y - p2.y))<1e-10 &&        min(p1.x, p2.y) <= p0.x&&max(p1.x, p1.x) >= p0.x&&        min(p1.y, p2.y) <= p0.y&&max(p1.y, p2.y) >= p0.y        )        return true;    return false;}int main() {    point p1, p2, p3;    while (cin >> p1.x >> p1.y >> p2.x >> p2.y >> p3.x >> p3.y) {        cout << onSegment(p1, p2, p3) << endl;    }}