lineintersection.cpp

// lineintersection vibhor
 #include <iostream> 
using namespace std; 
struct Point { 
    int x, y; 
}; 
bool onSegment(Point p, Point q, Point r) { 
    if (q.x <= max(p.x, r.x) && q.x >= min(p.x, r.x) && 
        q.y <= max(p.y, r.y) && q.y >= min(p.y, r.y)) 
       return true; 
    return false; 
} 
int orientation(Point p, Point q, Point r) { 
    int val = (q.y - p.y) * (r.x - q.x) - 
              (q.x - p.x) * (r.y - q.y); 
    if (val == 0) return 0;  
    return (val > 0)? 1: 2; 
} 
bool doIntersect(Point p1, Point q1, Point p2, Point q2) { 
   
    int o1 = orientation(p1, q1, p2); 
    int o2 = orientation(p1, q1, q2); 
    int o3 = orientation(p2, q2, p1); 
    int o4 = orientation(p2, q2, q1); 
   
    if (o1 != o2 && o3 != o4) 
        return true; 
  
    if (o1 == 0 && onSegment(p1, p2, q1)) return true; 
   
    if (o2 == 0 && onSegment(p1, q2, q1)) return true; 
  
   
    if (o3 == 0 && onSegment(p2, p1, q2)) return true; 
  
 
    if (o4 == 0 && onSegment(p2, q1, q2)) return true; 
  
    return false; 
}  
int main() { 
  
    doIntersect(p1, q1, p2, q2)? cout << "Yes\n": cout << "No\n"; 
  
    doIntersect(p1, q1, p2, q2)? cout << "Yes\n": cout << "No\n"; 
  
    doIntersect(p1, q1, p2, q2)? cout << "Yes\n": cout << "No\n"; 
  
    return 0; 
}