using System;

using NUnit.Framework;

​

public class LineIntersectionTests

{

    [Test]

    public void GetIntersectionPoint_IntersectingLines_ReturnsIntersectionPoint()

    {

        // Arrange

        (double x, double y) p1 = (1, 2);

        (double a, double b) v1 = (1, 1);

        (double x, double y) p2 = (3, 1);

        (double a, double b) v2 = (-1, 1);

        (double x, double y) expected = (2, 3);

​

        // Act

        var result = LineIntersection.GetIntersectionPoint(p1, v1, p2, v2);

​

        // Assert

        Assert.That(result, Is.EqualTo(expected));

    }

​

    [Test]

    public void GetIntersectionPoint_ParallelLines_ReturnsNull()

    {

        // Arrange

        (double x, double y) p1 = (1, 2);

        (double a, double b) v1 = (1, 1);

        (double x, double y) p2 = (3, 4);

        (double a, double b) v2 = (1, 1);

​

        // Act

        var result = LineIntersection.GetIntersectionPoint(p1, v1, p2, v2);

​

        // Assert

        Assert.That(result, Is.Null);

    }

}

​

public class LineIntersection

{

    public static (double x, double y)? GetIntersectionPoint(

        (double x, double y) p1, (double a, double b) v1,

        (double x, double y) p2, (double a, double b) v2)

    {

        double det = v1.a * v2.b - v1.b * v2.a;

​

        if (Math.Abs(det) < 1e-6)

        {

            return null; // Lines are parallel

        }

​

        double t = ((p2.x - p1.x) * v2.b - (p2.y - p1.y) * v2.a) / det;

​

        double x = p1.x + t * v1.a;

        double y = p1.y + t * v1.b;

​

        return (x, y);

    }

​

    public static void Main(string[] args)

    {

        // Example usage:

        (double x, double y) p1 = (1, 2);

        (double a, double b) v1 = (1, 1);

        (double x, double y) p2 = (3, 1);

        (double a, double b) v2 = (-1, 1);

​

        var intersection = GetIntersectionPoint(p1, v1, p2, v2);

​

        if (intersection.HasValue)

        {

            Console.WriteLine($"Intersection point: ({intersection.Value.x}, {intersection.Value.y})");

        }

        else

        {

            Console.WriteLine("Lines are parallel.");

        }

    }

}