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#include <iostream>
 
void swap(double &a, double &b)
{
    double temp = a;
    a = b;
    b = temp;
}
 
void Gauss(double **A, double *B, unsigned dim)
{
    for (unsigned k = 0; k < dim; ++k)
    {
        if (A[k][k] == 0.0)
        {
            for (unsigned i = k + 1; i < dim; ++i)
            {
                if (A[i][k] != 0.0)
                {
                    for (unsigned j = 0; j < dim; ++j)
                        swap(A[i][j], A[k][j]);
 
                    swap(B[i], B[k]);
 
                    break;
                }
            }
        }
 
        double div = A[k][k];
 
        for (unsigned j = 0; j < dim; ++j)
            A[k][j] /= div;
 
        B[k] /= div;
 
        for (unsigned i = k + 1; i < dim; ++i)
        {
            double multi = A[i][k];
 
            for (unsigned j = 0; j < dim; ++j)
                A[i][j] -= multi * A[k][j];
 
            B[i] -= multi * B[k];
        }
    }
 
    for (unsigned k = dim - 1; k > 0; --k)
    {
        for (unsigned i = k - 1; i + 1 > 0; --i)
        {
            double multi = A[i][k];
 
            for (unsigned j = 0; j < dim; ++j)
                A[i][j] -= multi * A[k][j];
 
            B[i] -= multi * B[k];
        }
    }
}
 
int main()
{
    double *A[4];
    double B[4] = {4.3, 6.8, -1.8, 7.2};
 
    for (int i = 0; i < 4; ++i)
        A[i] = new double [4];
 
    A[0][0] = 4.4; A[0][1] = -2.5; A[0][2] = 19.2; A[0][3] = -10.8;
    A[1][0] = 5.5; A[1][1] = -9.3; A[1][2] = -14.2; A[1][3] = 13.2;
    A[2][0] = 7.1; A[2][1] = -11.5; A[2][2] = 5.3; A[2][3] = -6.7;
    A[3][0] = 14.2; A[3][1] = 23.4; A[3][2] = -8.8; A[3][3] = 5.3;
 
    Gauss(A, B, 4);
 
    std::cout << "X = {"
              << B[0] << ", "
              << B[1] << ", "
              << B[2] << ", "
              << B[3]
              << "}" << std::endl;
 
    for (int i = 0; i < 4; ++i)
        delete [] A[i];
 
    return 0;
}

#include <iostream>
 
void transpose(double **A, double **result, int rows, int cols)
{
    for (int i = 0; i < cols; ++i)
        for (int j = 0; j < rows; ++j)
            result[i][j] = A[j][i];
}
 
void multiply(double **A, double **B, double **result, int n, int m, int p)
{
    for (int i = 0; i < n; ++i)
    {
        for (int j = 0; j < p; ++j)
        {
            result[i][j] = 0.0;
 
            for (int k = 0; k < m; ++k)
                result[i][j] += A[i][k] * B[k][j];
        }
    }
}
 
int main()
{
    double **Y, **X, **XT;
    int n, m;
 
    std::cout << "Enter n: ";
    std::cin >> n;
    std::cout << "Enter m: ";
    std::cin >> m;
 
    Y = new double *[n];
 
    for (int i = 0; i < n; ++i)
        Y[i] = new double [n];
 
    X = new double *[n];
 
    for (int i = 0; i < n; ++i)
        X[i] = new double [m];
 
    XT = new double *[m];
 
    for (int i = 0; i < m; ++i)
        XT[i] = new double [n];
 
    for (int i = 0; i < n; ++i)
    {
        for (int j = 0; j < m; ++j)
        {
            std::cout << "X[" << i << "][" << j << "] = ";
            std::cin >> X[i][j];
        }
    }
 
    transpose(X, XT, n, m);
    multiply(X, XT, Y, n, m, n);
 
    for (int i = 0; i < n; ++i)
    {
        for (int j = 0; j < n; ++j)
            std::cout << Y[i][j] << "  ";
 
        std::cout << std::endl;
    }
 
    for (int i = 0; i < n; ++i)
        delete [] Y[i];
 
    delete [] Y;
 
    for (int i = 0; i < n; ++i)
        delete [] X[i];
 
    delete [] X;
 
    for (int i = 0; i < m; ++i)
        delete [] XT[i];
 
    delete [] XT;
 
    return 0;
}