IterationMethod

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;


namespace Gauss
{
    class Program
    {
       static List<List<double>> GetMatrix(List<double> b)
        {
            StreamReader fin = new StreamReader("input.txt");
            int n = int.Parse(fin.ReadLine());

            List<List<double>> matrix = new List<List<double>>();

            for (int i = 0; i < n; i++)
            {
                List<double> tmp = new List<double>();
                string[] line = fin.ReadLine().Split(' ');
                for(int j = 0; j < n; j++)
                    tmp.Add(double.Parse(line[j]));
                matrix.Add(tmp);
            }

            string[] vector = fin.ReadLine().Split(' ');
            for (int j = 0; j < n; j++)
                b.Add(double.Parse(vector[j]));

            fin.Close();

            return matrix;
        }

        static void IterationMethod()
        {
            List<double> vector = new List<double>();
            List<List<double>> matrix = GetMatrix(vector);
            List<double>bVector = new List<double>();
            List<List<double>> x = new List<List<double>>();
            List<double> steepVector = new List<double>();
            List<List<double>> multiplyMatrix = new List<List<double>>();
            double e = 0.000001;
            multiplyMatrix = matrix;
            for (int i = 0; i < matrix.Count; i++)
            {
                bVector.Add(vector[i] / matrix[i][i]);
                for (int j = 0; j < matrix.Count; j++)
                    if (i == j)     multiplyMatrix[i][j] = 0;
                    else    multiplyMatrix[i][j] = -matrix[i][j] / matrix[i][i];
            }

            for (int i = 0; i < vector.Count; i++)
                steepVector.Add(vector[i]);

            int count = 0;

            x.Add(steepVector);

            PrintVector(x[x.Count - 1], ++count);

            steepVector = multiplyMatrixWithVector(matrix, x[x.Count - 1]);
            SumVectors(steepVector, vector);
            x.Add(steepVector);

            PrintVector(x[x.Count - 1], ++count);

            while (vectorsNorm(x[x.Count - 2], x[x.Count - 1]) > e)
            {
                steepVector = multiplyMatrixWithVector(matrix, x[x.Count - 1]);
                SumVectors(steepVector, vector);
                x.Add(steepVector);
                PrintVector(x[x.Count - 1], ++count);
            }

            Console.Write("Finally result: ");
            for(int i = 0; i < x[x.Count - 1].Count; i++)
                Console.Write("{0} ", x[x.Count - 1][i]);
            Console.WriteLine();
        }

        static void PrintVector(List<double> vector, int count)
        {
            Console.Write("Step #{0}: ", count);
            for (int i = 0; i < vector.Count; i++)
                Console.Write("{0} ", vector[i]);
            Console.WriteLine();
        }

        static List<double> multiplyMatrixWithVector(List<List<double>> matrix, List<double> vector)
        {
            List<double> resultVector = new List<double>();
            for (int i = 0; i < matrix.Count; i++)
            {
                resultVector.Add(0);
                for (int j = 0; j < vector.Count; j++)
                    resultVector[i] += matrix[i][j] * vector[j];
            }

            return resultVector;
        }

        static void SumVectors(List<double> firstVector, List<double> secondVector)
        {
            for (int i = 0; i < firstVector.Count; i++)
                firstVector[i] += secondVector[i];
        }

        public static double vectorsNorm(List<double> firstVector, List<double> secondVector)
        {
            double maxNorm = -1;

            for (int i = 0; i < firstVector.Count; i++)
                if (Math.Abs(secondVector[i] - firstVector[i]) > maxNorm)
                    maxNorm = Math.Abs(secondVector[i] - firstVector[i]);

            return maxNorm;
        }
        static void Main(string[] args)
        {
            IterationMethod();
        }
    }
}