2本の線が交差するかどうかをテストするために上記のプリミティブの下で使用するC++プログラム

これは、2本の線が交差するかどうかをテストするために上記のプリミティブの下で使用するC++プログラムです。線が線分と交差するかどうかをテストするために使用できます。これは、セグメントの一方の端点が線の左側にあり、もう一方の端点が右側にある場合にのみ行われます。

アルゴリズム

Begin
   For generating equation of the first line, generate random numbers for coefficient of x and y by using rand at every time of compilation.
   For generating equation of the second line, generate random numbers for coefficient of x and y by using rand at every time of compilation.
   Find the segment of line 1 as Y1.
   if (Y1 < 0)
      Find the segment of line 2
   if (Y2 >= 0)
      print they are intersecting.
   else if (Y2 < 0)
      print they are not intersecting.
   else if (Y1 >0)
      Find the segment of line 2
   if (Y2 <= 0)
      print they are intersecting.
   else if (Y2 >0)
      print they are not intersecting.
End.

サンプルコード

#include<time.h>
#include<stdlib.h>
#include<iostream>
#include<math.h>

using namespace std;
const int L = 2;
const int H= 20;
int main(int argc, char **argv) {
   time_t s;
   time(&s);
   srand((unsigned int) s);

   int x1, x2, y1, y2;
   x1 = rand() % (H - L+ 1) + L;
   x2 = rand() % (H - L+ 1) + L;
   y1 = rand() % (H- L+ 1) + L;
   y2 = rand() % (H - L + 1) + L;

   cout << "The Equation of the 1st line is : (" << (y2 - y1) << ")x+(" << (x1 - x2) << ")y+(" << (x2 * y1 - x1 * y2) << ") = 0\n";

   int p1, p2, q1, q2;
   p1 = rand() % (H- L+ 1) + L;
   p2 = rand() % (H- L + 1) + L;
   q1 = rand() % (H - L + 1) + L;
   q2 = rand() % (H - L + 1) + L;

   cout << "The Equation of the 2nd line is : (" << (q2 - q1) << ")x+(" << (p1 - p2) << ")y+(" << (p2 * q1 - p1 * q2) << ") = 0\n";

   int Y1 = (y2 - y1) * p1 + (x1 - x2) * q1 + (x2 * y1 - x1 * y2); //Y1 segment
   if (Y1 < 0) {
      int Y2 = (y2 - y1) * p2 + (x1 - x2) * q2 + (x2 * y1 - x1 * y2); //Y2 segment
   if (Y2 >= 0)
      cout << "Lines are intersecting";
   else if (Y2 < 0)
      cout << "Lines are not intersecting";
   } else if (Y1 >0) {
      int Y2 = (y2 - y1) * p2 + (x1 - x2) * q2 + (x2 * y1 - x1 * y2);
      if (Y2 <= 0)
         cout << "Lines are intersecting";
      else if (Y2 >0)
         cout << "Lines are not intersecting";
   } else
      cout << "The point lies on the line";
   return 0;
}

出力

The Equation of the 1st line is : (-3)x+(2)y+(1) = 0
The Equation of the 2nd line is : (-5)x+(-5)y+(130) = 0
Lines are intersecting


The Equation of the 1st line is : (-1)x+(7)y+(-15) = 0
The Equation of the 2nd line is : (-4)x+(4)y+(-8) = 0
Lines are not intersecting