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  1. using System;
  2. using System.Drawing;
  3.  
  4. public class Test
  5. {
  6. 	public static void Main()
  7. 	{
  8.     	Console.WriteLine(LinesIntersect("0,0-2,8:8,0-0,20")); // No intersect
  9.  
  10.     	Console.WriteLine(LinesIntersect("0,10-2,0:10,0-0,5")); // Intersect
  11.  
  12.         Console.WriteLine(LinesIntersect("0,0-0,10:2,0-2,10")); // Parallel, vertical
  13.         Console.WriteLine(LinesIntersect("0,0-5,5:2,0-7,5")); // Parallel, diagonal
  14.  
  15.         Console.WriteLine(LinesIntersect("0,0-5,5:2,2-7,7")); // Collinear, overlap
  16.         Console.WriteLine(LinesIntersect("0,0-5,5:7,7-10,10")); // Collinear, no overlap
  17.  
  18. 	}
  19.  
  20.     // Utility wrapper around LinesIntersect, expecting a string in the form:
  21.     // A-B:C-D
  22.     // Where A, B, C and D are cartesian coordinates in the form:
  23.     // XX.XX,YY.YY
  24.     static bool LinesIntersect(string s)
  25.     {
  26.         PointF A, B, C, D;
  27.  
  28.         string[] split = s.Split(',', '-', ':');
  29.  
  30.         A = new PointF(float.Parse(split[0]), float.Parse(split[1]));
  31.         B = new PointF(float.Parse(split[2]), float.Parse(split[3]));
  32.         C = new PointF(float.Parse(split[4]), float.Parse(split[5]));
  33.         D = new PointF(float.Parse(split[6]), float.Parse(split[7]));
  34.  
  35.         return LinesIntersect(A, B, C, D);
  36.     }
  37.  
  38.     // Determines if the lines AB and CD intersect.
  39. 	static bool LinesIntersect(PointF A, PointF B, PointF C, PointF D)
  40. 	{
  41. 		PointF CmP = new PointF(C.X - A.X, C.Y - A.Y);
  42. 		PointF r = new PointF(B.X - A.X, B.Y - A.Y);
  43. 		PointF s = new PointF(D.X - C.X, D.Y - C.Y);
  44.  
  45. 		float CmPxr = CmP.X * r.Y - CmP.Y * r.X;
  46. 		float CmPxs = CmP.X * s.Y - CmP.Y * s.X;
  47. 		float rxs = r.X * s.Y - r.Y * s.X;
  48.  
  49. 		if (CmPxr == 0f)
  50. 		{
  51. 			// Lines are collinear, and so intersect if they have any overlap
  52.  
  53. 			return ((C.X - A.X < 0f) != (C.X - B.X < 0f))
  54. 				|| ((C.Y - A.Y < 0f) != (C.Y - B.Y < 0f));
  55. 		}
  56.  
  57. 		if (rxs == 0f)
  58. 			return false; // Lines are parallel.
  59.  
  60. 		float rxsr = 1f / rxs;
  61. 		float t = CmPxs * rxsr;
  62. 		float u = CmPxr * rxsr;
  63.  
  64. 		return (t >= 0f) && (t <= 1f) && (u >= 0f) && (u <= 1f);
  65. 	}
  66. }
Success #stdin #stdout 0.03s 33808KB
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stdin
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Standard input is empty
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False
True
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https://ideone.com/PnPJgb
language:
C# (gmcs 5.20.1)
created:
11 years ago
visibility:
secret

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