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  1. 	import java.util.Arrays;
  2. 	import java.util.List;
  3.  
  4. 	class LineSegment {
  5. 		public static class Point {
  6. 			public final double x;
  7. 			public final double y;
  8.  
  9. 			public Point(double x, double y) {
  10. 				this.x = x;
  11. 				this.y = y;
  12. 			}
  13.  
  14. 			public String toString() {
  15. 				return "(" + x + "," + y + ")";
  16. 			}
  17. 		}
  18.  
  19. 		public static void main(String[] args) {
  20. 			LineSegment segment = new LineSegment(new Point(0, 3), new Point(2, 0));
  21. 			List<Point> pointList =
  22. 					Arrays.asList(new Point[] { new Point(-5, 3), new Point(1, 1),
  23. 							new Point(2, 3), new Point(0, 5) });
  24.  
  25. 			Point answer = segment.closestPoint(pointList);
  26. 			System.out.println("The closest point is: " + answer);
  27. 		}
  28.  
  29. 		private static double sqr(double x) {
  30. 			return x * x;
  31. 		}
  32.  
  33. 		private static double distanceSquared(Point v, Point w) {
  34. 			return sqr(v.x - w.x) + sqr(v.y - w.y);
  35. 		}
  36.  
  37. 		private final Point firstSegPoint;
  38. 		private final Point secondSegPoint;
  39. 		private final double segmentDistance;
  40. 		private double xDifference;
  41. 		private double yDifference;
  42.  
  43. 		public LineSegment(Point firstSegPoint, Point secondSegPoint) {
  44. 			this.firstSegPoint = firstSegPoint;
  45. 			this.secondSegPoint = secondSegPoint;
  46. 			this.segmentDistance = distanceSquared(firstSegPoint, secondSegPoint);
  47. 			this.xDifference = secondSegPoint.x - firstSegPoint.x;
  48. 			this.yDifference = secondSegPoint.y - firstSegPoint.y;
  49. 		}
  50.  
  51. 		public Point closestPoint(List<Point> pointList) {
  52. 			double minDistance = Double.POSITIVE_INFINITY;
  53. 			Point answer = null;
  54.  
  55. 			for (Point point : pointList) {
  56. 				double distSquared = distToSegmentSquared(point);
  57. 				if (distSquared < minDistance) {
  58. 					answer = point;
  59. 					minDistance = distSquared;
  60. 				}
  61. 			}
  62.  
  63. 			return answer;
  64. 		}
  65.  
  66. 		private double distToSegmentSquared(Point input) {
  67. 			if (segmentDistance == 0)
  68. 				return distanceSquared(input, firstSegPoint);
  69.  
  70. 			double xComponent = (input.x - firstSegPoint.x) * xDifference;
  71. 			double yComponent = (input.y - firstSegPoint.y) * yDifference;
  72. 			double t = (xComponent + yComponent) / segmentDistance;
  73. 			if (closestPointIsFirst(t))
  74. 				return distanceSquared(input, firstSegPoint);
  75. 			if (closestPointIsSecond(t))
  76. 				return distanceSquared(input, secondSegPoint);
  77. 			Point closestPointOnLine =
  78. 					new Point(firstSegPoint.x + t * xDifference, firstSegPoint.y
  79. 							+ t * yDifference);
  80. 			return distanceSquared(input, closestPointOnLine);
  81. 		}
  82.  
  83. 		private boolean closestPointIsFirst(double t) {
  84. 			return t < 0;
  85. 		}
  86.  
  87. 		private boolean closestPointIsSecond(double t) {
  88. 			return t > 1;
  89. 		}
  90. 	}
  91.  
  92.  
Success #stdin #stdout 0.11s 320256KB
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stdin
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Standard input is empty
stdout
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The closest point is: (1.0,1.0)
https://ideone.com/fBFwda
language:
Java (HotSpot 12)
created:
9 years ago
visibility:
public

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