using System;

namespace Test102
{
    public struct PointStruct
    {
        public double X;
        public double Y;

        public PointStruct(double x, double y)
        {
            X = x;
            Y = y;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            PointStruct p1 = new PointStruct(270, 80);
            PointStruct p2 = new PointStruct(400, 50);
            PointStruct p3 = new PointStruct(300, 50);
            PointStruct p4 = new PointStruct(500, 50);

            double Xa;
            double Ya;
            double A1;
            double A2;
            double b1;
            double b2;

            //Должно выполняться условие p1.x <= p2.x и p3.x <= p4.x.
            if (p2.X < p1.X)
            {
                PointStruct tmp = p1;
                p1 = p2;
                p2 = tmp;
            }

            if (p4.X < p3.X)
            {
                PointStruct tmp = p3;
                p3 = p4;
                p4 = tmp;
            }

            //Для частного случая, если оба отрезка не вертикальны
            A1 = (double)(p1.Y - p2.Y) / (p1.X - p2.X);
            A2 = (double)(p3.Y - p4.Y) / (p3.X - p4.X);
            b1 = (double)p1.Y - A1 * p1.X;
            b2 = (double)p3.Y - A2 * p3.X;

            Console.WriteLine("A1: " + A1);
            Console.WriteLine("A2: " + A2);
            Console.WriteLine("b1: " + b1);
            Console.WriteLine("b2: " + b2);

            Console.WriteLine();

            if (A1 == A2)
            {
                Console.WriteLine("Отрезки параллельны");
            }
            else
            {
                Xa = (double)(b2 - b1) / (A1 - A2);
                Ya = (double)A1 * Xa + b1;
                Console.WriteLine("Xa: " + Xa);
                Console.WriteLine("Ya: " + Ya);

                Console.WriteLine();

                if ((Xa < Math.Max(p1.X, p3.X)) || (Xa > Math.Min(p2.X, p4.X)))
                {
                    Console.WriteLine("Не пересекаются");
                }
                else
                {
                    Console.WriteLine("Пересекаются");
                }
            }                     

            Console.ReadKey();
        }
    }
}