NM3 0

using System;

namespace ЧМ1
{
    public class function
    {
        public int x;
        public double y;
        public function(int a, double b)
        {
            x = a;
            y = b;
        }
    }
    class MainClass
    {
        public static double Sqinter(function [] a, int b)
        {
            double Yo = a[0].y + (a[0].y - a[1].y) * (b - a[0].x) / (a[0].x - a[1].x) + (a[0].y - a[1].y) * (b - a[1].x) * (b - a[0].x) / ((a[0].x - a[1].x) * (a[0].x - a[2].x)) - (a[1].y - a[2].y) * (b - a[1].x) * (b - a[0].x) / ((a[1].x-a[2].x) * (a[0].x-a[2].x));
            return Yo;
        }
        public static void Main(string[] args)
        {
            int[] X = new int[11] {5,10,15,20,25,30,40,50,60,70,80};
            double[] Y = new double[11] {43.7,48,51,53,56.1,58.2,62.5,67,70.8,74.2,77};
            double[] y = new double[3];
            double[] y1 = new double[3];
            int[] x = new int[3] { 13, 31, 65 };
            int[] ind = new int[3];
            function [] xi = new function [3];
            Console.WriteLine("Проведем контроль следующих точек: ");
            for (int i = 0; i < 3; i++)
            {
                Console.WriteLine("{0}. X = {1}", i + 1, x[i]);
            }
            for (int i = 0; i < 3; i++)
            {
                for (int r = 0; r < 11; r++)
                {
                    if (x[i] < X[r])
                    {
                        ind[i] = r;
                        break;
                    }
                }
            }
            int arg = 0;
            int lok = 0;
            int min = 0;
            Console.WriteLine("Вычисление ближайших значений аргумента");
            for (int i = 0; i < 3; i++)
            {
                arg = 0;
                lok = 0;
                min = 1;
                while (arg < 3)
                {
                    if (Math.Abs(x[i] - X[ind[i] + lok]) < Math.Abs(x[i] - X[ind[i] - min]))
                    {
                        xi[arg] = new function (X[ind[i] + lok],Y[ind[i]+lok]);
                        lok++;
                    }
                    else
                    {
                        xi[arg] = new function(X[ind[i] - min],Y[ind[i]-min]);
                        min++;
                    }
                    arg++;
                }
                Console.WriteLine("Ближайшие к точке X = {0}:", x[i]);
                for (int r = 0; r < 3; r++)
                {
                    Console.WriteLine("{0}. {1}", r + 1, xi[r].x);
                }
                //рассчет значения функции в точке
                y[i] = Sqinter(xi, x[i]);
            }
            Console.WriteLine();
            Console.WriteLine("Итог: ");
            Console.WriteLine();
            for (int i = 0; i < 3; i++)
            {
                Console.WriteLine("X = {0}  Y = {1:f2}", x[i], y[i]);
            }
        }
    }
}