gauss-jordan.cpp

    /*************** Gauss Jordan method for inverse matrix ********************/

    #include<iostream>
    using namespace std;
    int main()
    {
        int i, j, k, n;

        cout << "No of equations ? ";
       cin >> n;
       float a[10][10] = { 0 }, d;
        cout << "Read all coefficients of matrix " << endl;
        for (i = 1; i <= n; i++)
            for (j = 1; j <= n; j++)
                cin >> a[i][j];
        for (i = 1; i <= n; i++)
            for (j = 1; j <= 2 * n; j++)
                if (j == (i + n))
                    a[i][j] = 1;
        /************** partial pivoting **************/
        for (i = n; i > 1; i--)
        {
            if (a[i - 1][1] < a[i][1])
                for (j = 1; j <= n * 2; j++)
                {
                    d = a[i][j];
                    a[i][j] = a[i - 1][j];
                    a[i - 1][j] = d;
                }
        }
        /********** reducing to diagonal  matrix ***********/
        for (i = 1; i <= n; i++)
        {
            for (j = 1; j <= n * 2; j++)
                if (j != i)
               {
                  d = a[j][i] / a[i][i];
                    for (k = 1; k <= n * 2; k++)
                        a[j][k] -= a[i][k] * d;
                }
        }
        /************** reducing to unit matrix *************/
       for (i = 1; i <= n; i++)
        {
            d = a[i][i];
            for (j = 1; j <= n * 2; j++)
                a[i][j] = a[i][j] / d;
        }
        cout << "your solutions: " << endl;
        for (i = 1; i <= n; i++)
        {
            for (j = n + 1; j <= n * 2; j++)
                cout << a[i][j] << "    ";
            cout << endl;
        }
        return 0;
    }