SweepMethod

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


namespace Gauss
{
    class Program
    {
       static List<List<double>> GetMatrix()
        {
            StreamReader fin = new StreamReader("input.txt");
            int n = int.Parse(fin.ReadLine());
            int m = 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 < m; j++)
                    tmp.Add(double.Parse(line[j]));
                matrix.Add(tmp);
            }

            fin.Close();

            return matrix;
        }

        static void SweepMethod()
        {
            List<List<double>> matrix = GetMatrix();
            List<double> p = new List<double>();
            List<double> Q = new List<double>();
            RightSweep(matrix, p, Q);
            BackSweep(p, Q);
        }

        static void RightSweep(List<List<double>> matrix, List<double> p, List<double> Q)
        {
            p.Add(matrix[0][1] / (-matrix[0][0]));
            Q.Add(-(matrix[0][matrix.Count] / (-matrix[0][0])));

            for (int i = 1, j = 0; i < matrix.Count - 1; i++, j++)
            {
                p.Add(matrix[i][j + 2] / (-matrix[i][j + 1] - (matrix[i][j] * p[i - 1])));
                Q.Add((matrix[i][j] * Q[i - 1] - matrix[i][matrix.Count]) / (-matrix[i][j + 1] - (matrix[i][j] * p[i - 1])));
            }

            p.Add(0);
            Q.Add((matrix[matrix.Count - 1][matrix.Count - 2] * Q[Q.Count - 1] - matrix[matrix.Count - 1][matrix.Count])
                / ((-matrix[matrix.Count - 1][matrix.Count - 1]) - (matrix[matrix.Count - 1][matrix.Count - 2] * p[p.Count - 1])));

        }

        static void BackSweep(List<double> p, List<double> Q)
        {
            List<double> x = new List<double>();
            x.Add(Q[Q.Count - 1]);
            for (int i = Q.Count - 2; i >= 0; i--)
            {
                x.Add(p[i] * x[x.Count - 1] + Q[i]);
            }

            x.Reverse();
            foreach (double item in x)
                Console.Write("{0} ", item);
            Console.WriteLine();
        }

        static void Main(string[] args)
        {
            SweepMethod();
        }
    }
}