Determine whether two line segments are Intersection

Template (hdu1086)

SPAN style = "FONT-SIZE: 18px"> include <iostream> using namespace std; struct point {double x, y ;}; struct segment {point begin, end ;}; double min (double x, double y) {return x <y? X: y;} double max (double x, double y) {return x> y? X: y;} bool onsegment (point pi, point pj, point pk) // determines whether the point pk is on the pi pj of the online segment {if (min (pi. x, pj. x) <= pk. x & pk. x <= max (pi. x, pj. x) {if (min (pi. y, pj. y) <= pk. y & pk. y <= max (pi. y, pj. y) {return true ;}} return false;} double direction (point pi, point pj, point pk) // calculate the cross product {return (pi. x-pk.x) * (pi. y-pj.y)-(pi. y-pk.y) * (pi. x-pj.x);} bool judge (point p1, point p2, point p3, point p4) // determine whether the p1p2 and p3p4 line segments intersect {double d1 = direction (p3, p4, p1); double d2 = direction (p3, p4, p2); double d3 = direction (p1, p2, p3); double d4 = direction (p1, p2, p4 ); if (d1 * d2 <0 & d3 * d4 <0) return true; if (d1 = 0 & onsegment (p3, p4, p1) return true; if (d2 = 0 & onsegment (p3, p4, p2) return true; if (d3 = 0 & onsegment (p1, p2, p3) return true; if (d4 = 0 & onsegment (p1, p2, p4) return true; return false;} int main () {int n, count; segment seg [101]; while (cin> n & n) {count = 0; for (int I = 1; I <= n; I ++) {cin> seg [I]. begin. x> seg [I]. begin. y> seg [I]. end. x> seg [I]. end. y ;}for (int I = 1; I <n; I ++) for (int j = I + 1; j <= n; j ++) {if (judge (seg [I]. begin, seg [I]. end, seg [j]. begin, seg [j]. end) {count ++ ;}}cout <count <endl ;}return 0 ;}</SPAN>