Gauss Elemination partial pivot

package gausselemination;

import java.util.Scanner;

public class GaussianElimination
{
    public void solve(double[][] A, double[] B)

    {

        int N = B.length;

        for (int k = 0; k < N; k++)

        {

            /** find pivot row **/

            int max = k;

            for (int i = k + 1; i < N; i++)

                if (Math.abs(A[i][k]) > Math.abs(A[max][k]))

                    max = i;



            /** swap row in A matrix **/

            double[] temp = A[k];

            A[k] = A[max];

            A[max] = temp;



            /** swap corresponding values in constants matrix **/

            double t = B[k];

            B[k] = B[max];

            B[max] = t;



            /** pivot within A and B **/

            for (int i = k + 1; i < N; i++)

            {

                double factor = A[i][k] / A[k][k];

                B[i] -= factor * B[k];

                for (int j = k; j < N; j++)

                    A[i][j] -= factor * A[k][j];

            }

        }



        /** Print row echelon form **/

        printRowEchelonForm(A, B);



        /** back substitution **/

        double[] solution = new double[N];

        for (int i = N - 1; i >= 0; i--)

        {

            double sum = 0.0;

            for (int j = i + 1; j < N; j++)

                sum += A[i][j] * solution[j];

            solution[i] = (B[i] - sum) / A[i][i];

        }

        /** Print solution **/

        printSolution(solution);

    }

    /** function to print in row    echleon form **/

    public void printRowEchelonForm(double[][] A, double[] B)

    {

        int N = B.length;

        System.out.println("\nRow Echelon form : ");

        for (int i = 0; i < N; i++)

           {

               for (int j = 0; j < N; j++)

                   System.out.printf("%.3f ", A[i][j]);

               System.out.printf("| %.3f\n", B[i]);

           }

           System.out.println();

    }

    /** function to print solution **/

    public void printSolution(double[] sol)

    {

        int N = sol.length;

        System.out.println("\nSolution : ");

        for (int i = 0; i < N; i++)

            System.out.printf("%.3f ", sol[i]);

        System.out.println();

    }
}

public class Main
{
    public static void main(String[] args)
    {
        Scanner scan = new Scanner(System.in);

        System.out.println("Gaussian Elimination Algorithm Test\n");

        /** Make an object of GaussianElimination class **/

        GaussianElimination ge = new GaussianElimination();



        System.out.println("\nEnter number of variables");

        int N = scan.nextInt();



        double[] B = new double[N];

        double[][] A = new double[N][N];



        System.out.println("\nEnter "+ N +" equations coefficients ");

        for (int i = 0; i < N; i++)

            for (int j = 0; j < N; j++)

                A[i][j] = scan.nextDouble();



        System.out.println("\nEnter "+ N +" solutions");

        for (int i = 0; i < N; i++)

            B[i] = scan.nextDouble();



        ge.solve(A,B);
    }
}