Line circle intersection: Difference between revisions
Added C#
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a segment starting at (7, 4) and ending at (11, 8) is/are:
[(8, 5)]</pre>
=={{header|C#}}==
{{trans|C++}}
<lang C#>using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
public static void Main()
{
Circle circle = ((3, -5), 3);
Line[] lines = {
((-10, 11), (10, -9)),
((-10, 11), (-11, 12), true),
((3, -2), (7, -2))
};
Print(circle, lines);
circle = ((0, 0), 4);
lines = new Line[] {
((0, -3), (0, 6)),
((0, -3), (0, 6), true)
};
Print(circle, lines);
circle = ((4, 2), 5);
lines = new Line[] {
((6, 3), (10, 7)),
((7, 4), (11, 8), true)
};
Print(circle, lines);
}
static void Print(Circle circle, Line[] lines)
{
Console.WriteLine($"Circle: {circle}");
foreach (var line in lines) {
Console.WriteLine($"\t{(line.IsSegment ? "Segment:" : "Line:")} {line}");
var points = Intersection(circle, line).ToList();
Console.WriteLine(points.Count == 0 ? "\t\tdo not intersect" : "\t\tintersect at " + string.Join(" and ", points));
}
Console.WriteLine();
}
static IEnumerable<Point> Intersection(Circle circle, Line line)
{
var intersection = LineIntersection(circle, line);
return line.IsSegment
? intersection.Where(p => p.CompareTo(line.P1) >= 0 && p.CompareTo(line.P2) <= 0)
: intersection;
static IEnumerable<Point> LineIntersection(Circle circle, Line line)
{
double x, y, A, B, C, D;
var (m, c) = (line.Slope, line.YIntercept);
var (p, q, r) = (circle.X, circle.Y, circle.Radius);
if (line.IsVertical) {
x = line.P1.X;
B = -2 * q;
C = p * p + q * q - r * r + x * x - 2 * p * x;
D = B * B - 4 * C;
if (D == 0) yield return (x, -q);
else if (D > 0) {
D = Math.Sqrt(D);
yield return (x, (-B - D) / 2);
yield return (x, (-B + D) / 2);
}
} else {
A = m * m + 1;
B = 2 * (m * c - m * q - p);
C = p * p + q * q - r * r + c * c - 2 * c * q;
D = B * B - 4 * A * C;
if (D == 0) {
x = -B / (2 * A);
y = m * x + c;
yield return (x, y);
} else if (D > 0) {
D = Math.Sqrt(D);
x = (-B - D) / (2 * A);
y = m * x + c;
yield return (x, y);
x = (-B + D) / (2 * A);
y = m * x + c;
yield return (x, y);
}
}
}
}
readonly struct Point : IComparable<Point>
{
public Point(double x, double y) => (X, Y) = (x, y);
public static implicit operator Point((double x, double y) p) => new Point(p.x, p.y);
public double X { get; }
public double Y { get; }
public int CompareTo(Point other)
{
int c = X.CompareTo(other.X);
if (c != 0) return c;
return Y.CompareTo(other.Y);
}
public override string ToString() => $"({X}, {Y})";
}
readonly struct Line
{
public Line(Point p1, Point p2, bool isSegment = false)
{
(P1, P2) = p2.CompareTo(p1) < 0 ? (p2, p1) : (p1, p2);
IsSegment = isSegment;
if (p1.X == p2.X) (Slope, YIntercept) = (double.PositiveInfinity, double.NaN);
else {
Slope = (P2.Y - P1.Y) / (P2.X - P1.X);
YIntercept = P2.Y - Slope * P2.X;
}
}
public static implicit operator Line((Point p1, Point p2) l) => new Line(l.p1, l.p2);
public static implicit operator Line((Point p1, Point p2, bool isSegment) l) => new Line(l.p1, l.p2, l.isSegment);
public Point P1 { get; }
public Point P2 { get; }
public double Slope { get; }
public double YIntercept { get; }
public bool IsSegment { get; }
public bool IsVertical => P1.X == P2.X;
public override string ToString() => $"[{P1}, {P2}]";
}
readonly struct Circle
{
public Circle(Point center, double radius) => (Center, Radius) = (center, radius);
public static implicit operator Circle((Point center, double radius) c) => new Circle(c.center, c.radius);
public Point Center { get; }
public double Radius { get; }
public double X => Center.X;
public double Y => Center.Y;
public override string ToString() => $"{{ C:{Center}, R:{Radius} }}";
}
}</lang>
{{out}}
<pre>Circle: { C:(3, -5), R:3 }
Line: [(-10, 11), (10, -9)]
intersect at (3, -2) and (6, -5)
Segment: [(-11, 12), (-10, 11)]
do not intersect
Line: [(3, -2), (7, -2)]
intersect at (3, -2)
Circle: { C:(0, 0), R:4 }
Line: [(0, -3), (0, 6)]
intersect at (0, -4) and (0, 4)
Segment: [(0, -3), (0, 6)]
intersect at (0, 4)
Circle: { C:(4, 2), R:5 }
Line: [(6, 3), (10, 7)]
intersect at (1, -2) and (8, 5)
Segment: [(7, 4), (11, 8)]
intersect at (8, 5)
</pre>
=={{header|D}}==
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